AGA Design Guide

7/29/2019 AGA Design Guide

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uideThe esign of Products to be ot-ip alvanized after abricati


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Table of ContentsIntroduction 2

Communication among esign Engineer, Architect,

abricator, & alvanizer 3

Materials uitable for alvanizing 3

Combining ifferent Materials and urfaces

ize & hape

Process Temperature & eat 7

Mechanical Properties of alvanized Steel

Strain-age Embrittlement

ydrogen Embrittlement

Minimizing istortion 9

Allowing for Proper rainage 10

Tubular abrications & ollow tructurals 10 Cleaning

Venting

andrail

ectangular Tube Truss

Pipe Truss

Pipe Columns Pipe irders Street ight & Transmission Poles

Box Sections

Tapered Signal Arm

Proper enting & rainage of Enclosed &emi- Enclosed abrications 1

Precautions for verlapping & Contacting urfaces 17

elding Procedures & elding lux emoval 18

Threaded Parts 19

Moving Parts 20

Additional esign Considerations 21

Masking

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Post alvanizing Considerations 22 Storage

Cleaning alvanized Steel

issimilar Metals

Temperature of se

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2010 American Galvanizers Association. he material provided herein has been developed to provide accurate and authoritative inormation about

ater-abrication hot-dip galvanized steel. his material provides general inormation only and is not intended as a substitute or competent proessionalexamination and veriication as to suitability and applicability. he inormation provided herein is not intended as a representation or warranty on the

part o the AGA. Anyone making use o this inormation assumes all liability arising rom such use.


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Introduction

Te galvanizing process has existed or more than 250years and has been a mainstay o North American industrysince the 1890s. Galvanizing is used throughout variousmarkets to provide steel with unmatched protection romthe ravages o corrosion. A wide range o steel products rom nails to highway guardrail to the Brooklyn Bridgessuspension wires to NASAs launch pad sound-suppressionsystem beneft rom galvanizings superior corrosion

protection properties.

Te uses o hot-dip galvanized steel continue to evolve,and new markets are emerging all the time. As with allmaterials and coatings, there are certain practices whichyield better quality fnished products. In order to meet theexpectations and demands o many dierent markets, it isimportant to be cognizant o these best design practices orsteel to be galvanized. Oten no or only minor adjustmentsto the design are necessary, and worth the extra time and/oreort up ront to alleviate certain uture headaches relatedto the utilization o other coating systems.

NTRODUCTION


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Communication among esign ngineer,

Architect, abricator, alvanizer

Corrosion protection begins at the drawing board, and regardlesso what protection system is specifed, it must be actored intothe products design. Similarly, all corrosion protection systemsrequire certain design details and proper planning to ensurethe highest quality coating. For hot-dip galvanizing, a totalimmersion process in molten zinc, the design engineer will

want to ensure all pieces are abricated suitably or the process.Most design principles necessary or success throughout thegalvanizing process are easily and readily ollowed, and in mostcases, ensure maximum corrosion protection. Incorporatingthese design practices along with those listed in ASM A 385Practice or Providing High Quality Zinc Coatings (Hot-Dip), willnot only produce optimum quality galvanized coatings, but alsohelp reduce costs and improve turnaround times.

One key to providing the best design or the hot-dip galvanizing

process is communication between the architect, engineer,abricator and galvanizer. Opening the lines o communicationearly in the design process can eliminate potential costly pitallslater in the process. A ew discussion topics good to cover whilethe project is being designed include:

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6OEFSTUBOEJOHUIFTFBTQFDUTPGUIFHBMWBOJ[JOHQSPDFTTBOEIPXthey can aect the coating and fnished products outcome willhelp ensure everyones expectations are met.

aterials uitable for alvanizing

Most iron-containing (errous) materials are suitable or EJQHBMWBOJ[JOH1MBJODBSCPOTUFFMVOEFSLTJ.and low alloy materials, hot-rolled steel, cold-rolled steel, cast ductile iron, cast iron, castings, stainless steel, and even weathsteel can be and are galvanized or enhanced corrosion protec)PXFWFS UIF NBUFSJBMT DIFNJDBM DPNQPTJUJPO JOVFODFTcharacteristics o the galvanized coating.

%VSJOH HBMWBOJ[JOH UIF JSPO JO UIF NBUFSJBM SFBDUT XJUImolten zinc to orm a series o zinc-iron alloy layers, whichcovered by a layer o iron-ree zinc. For most hot-rolled sthe zinc-iron alloy portion o the coating will represent 50-o the total coating thickness, with the ree zinc outer accounting or the balance (Figure 1).

Steel compositions vary depending on strength and serequirements. race elements in the steel (silicon, phosphaect the galvanizing process as well as the structure and appear

o the galvanized coating. Steels with these elements outsidthe recommended ranges are known in the galvanizing indas highly reactive steel, and may produce a coating compentirely, or almost entirely, o zinc-iron alloy layers (Figure 2)

Communication among...

...from the projects inception to its completion can optimize turnaroundtimes minimize costs and ensure superior quality hot-dip galvanized steel.

esign

Engineer/

Architect

abricator/

etaileralvanizer

igure 1 ypical zinc-iron alloy layers

igure 2 Atypical zinc-iron alloy layers

American alvanizers Association


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Atypical coatings produced rom reactive steels exhibitdierent coating characteristics than a typical galvanizedcoating such as:

Appearance: Te atypical galvanized coating may havea matte gray appearance and/or roughersurace due to the absence o the ree zinclayer. Te ree zinc layer present on typical

coatings imparts a shinier fnish toa galvanized coating.

Adherence: Te zinc-iron alloy coating tends to bethicker than a typical galvanized coating.In the rare situation where the coating isexcessively thick, there is the possibility odiminished adhesion under external stress(thermal gradients, sharp impact).

Reactive steels are still galvanized on a regular basis, and it ismportant to note dierences in appearance have no eect onthe corrosion protection aorded by the galvanized coating.Te perormance o the coating is based on the thickness othe zinc; thereore, oten the duller (and thicker) coatingsproduced by reactive steels last longer. Furthermore, allgalvanized coatings as they weather over time will develop auniorm matte gray appearance.

It is dicult to provide precise guidance in the area o steel

selection without qualiying all steel grades commerciallyBWBJMBCMF)PXFWFSUIFTFHVJEFMJOFTEJTDVTTFEXJMMBTTJTUZPVin selecting steels that provide good galvanized coatings.

t-FWFMTPGDBSCPOMFTTUIBOQIPTQIPSVTMFTTUIBO0.04%, or manganese less than 1.35% are benefcial

t4JMJDPOMFWFMTMFTTUIBOPSCFUXFFOare desirable

Silicon may be present in many steels commonly galvanizedeven though it is not a part o the steels controlled

composition, because silicon is used in the steel deoxidationprocess and is ound in continuously cast steel. Both siliconand phosphorous act as catalysts during the galvanizingprocess, resulting in rapid growth o zinc-iron alloy layers.

And even when both elements are individually held todesirable limits, the combined eect between them canstill produce an atypical coating o all or mostly zinc-ironBMMPZ MBZFST 8IFO QPTTJCMF ZPVS HBMWBOJ[FS TIPVME CFadvised o the grade o steel selected in order to determinewhether specialized galvanizing techniques are suggested.

Castings

)JHIRVBMJUZ DBTUJOHT BOEGPSHFEQBSUT BSFBMTPDPNNPOMZand successully galvanized. Te quality o the galvanizing isTUSPOHMZJOVFODFECZUIFRVBMJUZPGUIFDBTUJOH"TXJUIBMMsteel to be galvanized, cleanliness is very important to achieveDPNQMFUFMZ HBMWBOJ[FE DBTU JSPO PS TUFFM QBSUT )PXFWFSconventional cleaning processes employed by galvanizersdo not adequately clean castings because sand and other

teel Casting


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surace inclusions are not removed by chemical cleaning.Torough abrasive cleaning is the most eective method orremoving oundry sand and impurities. Te preerred way toclean the casting is by abrasive blasting, either grit-blastingor a combination o grit and shot. Cleaning is traditionallyperormed at the oundry beore shipment to the galvanizer.

Sound, stress-ree castings with good surace fnishes willproduce high-quality galvanized coatings. Te ollowing

design and preparation rules should be applied or castingsto be galvanized:

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t6TFMBSHFQBUUFSOOVNFSBMTBOEHFOFSPVTSBEJJUPGBDJMJUBUFabrasive cleaning

t4QFDJGZVOJGPSNXBMMTFDUJPOT/POVOJGPSNXBMMUIJDLOFTTJOcertain casting designs may lead to distortion and/or cracking.Cracking results rom stress developed as the temperaturePGUIFDBTUJOHJTJODSFBTFEEVSJOHHBMWBOJ[JOH6OJGPSNXBMMsections and a balanced design lowers stress.

Combining ifferent aterials urfaces

7BSZJOHTVSGBDFDPOEJUJPOTEJFSFOUGBCSJDBUJPONFUIPETPSerrous metals with special chemistries, when combined, makeit dicult to produce coatings with uniorm appearance. Tisis because dierent parameters or pickling (immersion time,solution concentrations, temperatures) and galvanizing (bathtemperatures, immersion time) are required or:

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manganese, or silicon

Many coatings such as paint and lacquer cannot be remrom the steel with the chemical cleaning process used ingalvanizing acility. As perectly cleaned steel is required ometallurgical reaction to occur in the galvanizing kettle, contaminants need to be removed mechanically rom the suprior to sending the abrication to the galvanizer.

Te use o old along with new steel, or castings with rsteel in the same assembly, should be avoided (Figure 38

assemblies o cast iron, cast steel, malleable iron, or rolled steeunavoidable, the entire assembly should be thoroughly abrablasted prior to pickling to give the best chance or producconsistent galvanized coating appearance.

arying steel chemistries create visually different

coatings as illustrated by this pipe assembly

igure 3 esults will not be consistent with a combinatio

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uctile iron pipe with

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Castings with

mild carbon steel

orged bolt with

machined threads

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surface conditions



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Similarly, excessively rusted, pitted, or orged steels shouldalso not be used in combination with new or machinedsuraces because the dierence in required pickling timeor suluric acid pickling baths can cause over-pickling oUIF OFX PS NBDIJOFE TVSGBDFT 8IFSF UIJT DPNCJOBUJPOis unavoidable, a thorough abrasive blast cleaning o theassembly (normally beore any machining is done) providesa more uniorm galvanized coating.

I abrasive blast cleaning is used to prepare a surace or

galvanizing, a coating thicker than normal will be producedor low silicon steel. Abrasive cleaning roughens the steelsurace and increases its surace area, resulting in increasedreactivity with the molten zinc.

Te best practice when combining dierent materialsand suraces is to galvanize separately and assemble atergalvanizing. Tis will help acilitate ecient turnaroundtimes in the process, eliminate over-pickling, and allowUIF QJFDFT UP CF NBUDIFE GPS BQQFBSBODF 8IFUIFS SVOthrough the galvanizing process joined or separately, the

dierences in appearance on assemblies containing steelswith varying surace condition do not aect the corrosionprotection. Furthermore, ater aging in the environment,all suraces will exhibit a uniorm matte gray appearance.

ize hape

Another important consideration during the design processis the size and shape o the abrication. Because hot-dipgalvanizing is a total immersion process, the design musttake into consideration the capacity o the galvanizingkettle; thereore, it is wise to veriy kettle constraints with

your galvanizer early in the design process.Almost any component can be galvanizedby designing and abricating in modulessuitable or available galvanizingacilities. Te average kettle lengthin North America is 40 eet (13m),and there are many kettles between50-60 eet (15.24 m - 18.28 m).Kettle dimensions and contactinormation or all member

galvanizers are available atwww.galvanizeit.org/galvanizers.

-BSHFTUSVDUVSFTEFTJHOFEJONPEVMFTor sub-units to accommodate thegalvanizing kettle oten provideadditional savings in manuacturing andassembly because they simpliy handlingand transportation. Te sub-units can beconnected ater galvanizing by feld-welding orbolting. Alternatively, i an item is too large or total

immersion in the kettle, but more than hal o the item willft into the kettle, the piece may be progressively dipped.1SPHSFTTJWFEJQQJOHJTBDDPNQMJTIFECZEJQQJOHFBDIFOEPGthe article sequentially to coat the entire item. Consult yourgalvanizer before planning to progressively dip.

Considering size and shape, as well as weight, is also importantdue to material handling techniques used in galvanizing plants.Te steel is moved through the process by the use o hoists andoverhead cranes. Small items, less than 30 (76 cm) in length,are requently galvanized in perorated baskets. Te baskets arethen centriuged or spun to throw o excess zinc, delivering

smoother coatings. Fasteners, small brackets, and clips typiywork handled in baskets.

rogressive dipping - galvanizing oversized pieces $SHUIRUDWHGEDVNHWOOHGZLWKEROWVLVSODFHG

in a centrifuge to spin off excess zinc


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-BSHFBTTFNCMJFTBSFVTVBMMZTVQQPSUFECZDIBJOslings or by liting fxtures. Special jigs

and racks are also commonly used tosimultaneously galvanize large numbersPG TJNJMBS JUFNT 1SPWJEJOH MJGUJOH

points where possible will reduce oreliminate chain or wire marks thatcan be let on an item when noliting points are present. I noliting points are provided, any

marks, which are usually ullygalvanized, can be touched upi desired or aesthetic reasons.

It is also good practice to discussthe weight-handling capacity with

the galvanizer to ensure capacity orthe best places to put liting points.

In addition to liting points, largepipe sections, open-top tanks, and similar

structures may beneft rom temporary bracingto maintain their shape during handling.

rocess emperature/eat

%VSJOH UIF IPUEJQ HBMWBOJ[JOH QSPDFTT TUFFM JT IFBUFE UPapproximately 830 F (443 C) or the galvanizing reactionUP PDDVS &WFSZ UJNF TUFFM JT IFBUFE BOE DPPMFE TUSFTT JTadded to the abrication. Tereore, there are some designconsiderations to be aware o to help reduce any issues withthe heating o the galvanizing process.

echanical roperties of alvanized teel

Te hot-dip galvanizing process produces no signifcantchanges in the mechanical properties o the structural steelscommonly galvanized throughout the world. Te mechanicalproperties o 19 structural steels rom major industrialcountries were investigated beore and ater galvanizing ina our-year research project o the BNF Metals echnology$FOUSF6,VOEFSUIFTQPOTPSTIJQPGUIF*OUFSOBUJPOBM-FBE;JOD3FTFBSDI0SHBOJ[BUJPO*-;304UFFMTDPOGPSNJOHUPASM Standard Specifcations A 36 and A 572 Grade 60 andCanadian Standards Association (CSA) Specifcations G 40.8and G 40.12 were included in this study.

Te BNF report, Galvanizing o Structural Steels and TeirWeldments*-;30DPODMVEFT i UIFHBMWBOJ[JOHprocess has no eect on the tensile, bend or impact propertieso any o the structural steels investigated when these aregalvanized in the as manuactured condition.

Strain-Age Embrittlement

Many structures and parts are abricated using cold-rolled steel orcold-working techniques. In some instances, severe cold-workingNBZMFBEUPUIFTUFFMCFDPNJOHTUSBJOBHFFNCSJUUMFE8IJMFDPME

working increases the possibility o strain-age embrittlement, it

may not be evident until ater galvanizing. Tis occurs becauseaging is relatively slow at ambient temperatures, but more rapid atthe elevated temperature o the galvanizing bath.

Any orm o cold-working reduces steels ductility. Operationssuch as punching holes, notching, producing fllets o smallradii, shearing, or sharp bending (Figure 4) may lead to strain-age embrittlement o susceptible steels. Cold-worked steels lessthan 1/8-inch (3 mm) thick that are subsequently galvanizedare unlikely to experience strain-age embrittlement. Since cold-working is the strongest contributing actor to the embrittlemento galvanized steel, these tips (next page) are recommended toreduce the incidence o strain-age embrittlement.

ot-dip galvanizing cold-worked steel is very

successful when following suggested guidelines

referred esign

igure 4 Avoid severe cold-working



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ASM A 143, Saeguarding Against Embrittlemento Hot-Dip Galvanized Structural Steel Products andProcedure or Detecting Embrittlement, and CSASpecifcation G 164, Hot-Dip Galvanizing o IrregularlyShaped Articles, provide guidance on cold-workingBOETUSFTTSFMJFWJOHQSPDFEVSFT)PXFWFSJUJTCFTUUPavoid severe cold-working o susceptible steels. I thereis concern with possible loss o ductility due to strain-

age embrittlement, advise your galvanizer. A samplequantity o the cold-ormed items should be galvanizedand tested beore urther commitment.

ydrogen mbrittlement

)ZESPHFOFNCSJUUMFNFOUJTBEVDUJMFUPCSJUUMFDIBOHFUIBUPDDVST JODFSUBJO IJHITUSFOHUI TUFFMT)ZESPHFOembrittlement can occur when the hydrogen releasedduring the pickling process is absorbed by the steel andbecomes trapped in the grain boundaries. Normally, atgalvanizing temperatures, hydrogen is expelled romthe steel.

Although hydrogen embrittlement is uncommon,precautions should be taken to avoid it, particularly i thesteel involved has an ultimate tensile strength exceeding QTJ .1B *GIJHITUSFOHUI TUFFMT BSF UPbe processed, grit-blasting instead o acid-pickling isrecommended in order to minimize the introduction ogaseous hydrogen during the pickling process.

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transition temperature and galvanizing (heating

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is required to be less than 3x, the material should

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may be caused during shearing or punching

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should be punched undersize and then reamed

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ips to educe

train-Age mbrittlement

8


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inimizing istortion

Some abricated assemblies may distort at galvanizingtemperature as a result o relieving stresses induced duringsteel production and in subsequent abricating operations. Forexample, a channel rame with a plate should be galvanizedseparately and bolted later rather than welded together beoregalvanizing, or it can be welded ater galvanizing.

Guidelines or minimizing distortion and warpage provided in ASM A 384, Saeguarding Against WarpageDistortion During Hot-Dip Galvanizing o Steel AssembliesCSA Specifcation G 164, Hot Dip Galvanizing o IrreguShaped Articles.

ips for inimizing istortion

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recommendations

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igure 5 Avoid uneven thickness at joints

igure 6 emporary Bracing

Channel frame(typically fabricated toe-out)

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rough



12/28

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For eective galvanizing, cleaning solutions and molten zincNVTUPXXJUIPVUVOEVFSFTJTUBODFJOUPPWFSUISPVHIBOEut o the abricated article. Failure to provide or this ree,VOJNQFEFEPXDBOSFTVMUJODPNQMJDBUJPOTGPSUIFHBMWBOJ[FSnd the customer. Improper drainage design results in poorppearance, bare spots, and excessive build-up o zinc. All these are unnecessary and costly, and another example why communication throughout the project is key.

A ew common abrications where drainage is important areusset plates, stieners, end-plates, and bracing. Following theseest design practices will help ensure the highest quality coatings:

8IFSFHVTTFUQMBUFTBSFVTFEHFOFSPVTMZDSPQQFEDPSOFSTQSPWJEFGPSGSFFESBJOBHF8IFODSPQQJOHHVTTFUQMBUFTJTnot possible, holes at least 1/2-inch (13 mm) in diametermust be placed in the plates as close to the corners aspossible (Figure 7).

5P FOTVSF VOJNQFEFE PX PG TPMVUJPOT BMM TUJFOFSTgussets, and bracing should be cropped a minimumo 3/4-inch (19 mm) (Figure 8 1SPWJEF IPMFT BU MFBTU1/2-inch (13 mm) in diameter in end-plates on rolled steelshapes to allow molten zinc access during immersion in thegalvanizing bath and drainage during withdrawal.

Alternatively, holes at least 1/2-inch (13 mm) in diametercan be placed in the web within 1/4-inch (6 mm) o theend-plate. o acilitate drainage, end-plates shouldhave holes placed as close to interior corners aspossible (Figure 9).

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ubular assemblies (handrails, pipe columns, pipe girders,street light poles, transmission poles, pipe trusses, signbridges) are commonly galvanized because corrosionprotection is aorded to the interior and exterior o theproduct. o provide an optimal galvanized coating, hollowproducts require proper cleaning, venting, and draining.

Cleaning

As with all steel, pipe and other hollow materials must bethoroughly cleaned beore the molten zinc will metallurgically

CPOE XJUI UIF TUFFM 1JQF DBO QSFTFOU UXP TQFDJBM DMFBOJOHchallenges. First, the mill coating (varnish, lacquer, and similarmaterials) applied by pipe manuacturers requires extra timeand eort to remove at the galvanizing plant. Some galvanizersdo not have the capability to remove this coating. Some organicmill coating ormulations, both oreign and domestic, are

igure 8 Cropped gusset plate corners

Cropped Corners (preferred) oles close to corners (alternatively)

igure Cropped bracing

igure 9 oles in end-plate

10


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extremely dicult to remove with commoncleaning solutions, so blasting may be

required. Ordering uncoated pipeavoids costly attempts to remove

these mill coatings. In some cases,it may be more cost eective tosubstitute tube or pipe.

Second, welding around millcoatings burns and carbonizes

the varnish in the surroundingareas and cannot be removed

by the normal cleaning processat a galvanizer. Tis soot must

be removed by blasting or othermechanical cleaning methods prior to

delivering steel to the galvanizing acility.

enting

Te primary reason or vent and drain holes is to allow air

to be evacuated, permitting the object to be completelyJNNFSTFE JOUP DMFBOJOH TPMVUJPOT BOE NPMUFO [JOD 1SPQFShole sizing and location make it saer to galvanize and providethe optimal fnish. Te secondary reason is to prevent damageto the parts. Any pickling solutions or rinse waters that mightbe trapped in a blind or closed joining connection will beconverted to superheated steam or gas and can develop aQSFTTVSFPGVQUPQTJ.1BXIFOJNNFSTFEJOmolten zinc. Not only is there risk o damage to the abricationbeing galvanized, but there also is risk o serious hazard togalvanizing personnel and equipment.

8IFOUIFGBCSJDBUJPOJT MPXFSFEJOUP UIFDMFBOJOHTPMVUJPOTBOE[JODBJSBOEGSPUIZVYFTNVTUCFBMMPXFEUPPXVQXBSEand completely out. Cleaning solutions and molten zincNVTUCFBMMPXFEUPPXJOBOEDPNQMFUFMZXFUUIFTVSGBDFTTen, when the structure is raised rom the bath, no solutionsshould be trapped inside. Consequently, ample passagewaysBMMPXJOHVOJNQFEFEPXJOUPBOEPVUPGUIFQBSUNVTUCFEFTJHOFEJOUPBTTFNCMJFT1SPQFSHBMWBOJ[JOHSFTVMUTXIFOUIFinside and outside o a product are completely cleaned andzinc-coated.

Items are immersed and withdrawn rom the galvanizingkettle at an angle; thus, the vent holes should be located atthe highest point and drain holes at the lowest. All sectionso abricated pipe-work should be interconnected with ullPQFOUFF PS NJUFS KPJOUT &BDI FODMPTFE TFDUJPO NVTU CFprovided with a vent hole at each end.

Most galvanizers preer to visually identiy ventingrom the outside, in order to veriy the adequacy o theventing as well as to determine that venting has not beenmistakenly omitted.

Some galvanizers may hesitate to process complicated passemblies unless all venting is visible on the outside readily accessible or inspection (Figure 10).

Base-plates and end-plates must be designed to aciliventing and draining. Fully cutting the plate provNJOJNVNPCTUSVDUJPOUPBGVMMGSFFPXJOUPBOEPVUPGpipe. Since this is not always possible, using vent holes in

plate oten provides the solution.

7FOUIPMFTBSFGSFRVFOUMZMFGUPQFOCVUDBOCFDMPTFEXJUIEDBQTPSQMVHTBGUFSHBMWBOJ[JOH7BSJPVTNFUIPETPGWFOUJOHacceptable (Figure 11), but the subsequent plugging o tholes should be kept in mind, where necessary or desired

It is recommended tubular structures be completely submein one dip into the galvanizing kettle. Tis minimizes poteninternal coating problems that, because o the size and sho the item, may be dicult to discover during inspection

rilled

hole

notch

Corner

cut

rilled

hole in

DQJH

igure 1 enting

igure 11 ent hole options



14/28

Te ollowing drawings illustrate recommended designsor tubular abrications and hollow structures. Te ventdimensions are the minimum required.

andrail (Figure 12 & 13

Figure 12illustrates the most desirable design or abricationso handrail or galvanizing. It shows internal venting as wellas the minimum amount o external vent holes.

&YUFSOBM WFOU IPMFTNVTU CF BT DMPTF UP UIFweld as possible and not less than 3/8-inch(9.5 mm) in diameter.

*OUFSOBMIPMFTTIPVMECFUIFGVMM*%PGUIFpipe or the best galvanizing quality and lowestgalvanizing cost.

7FOUIPMFTJOFOETFDUJPOTPSJOTJNJMBSTFDUJPOTmust be 1/2-inch (13 mm) in diameter.

&OET TIPVME CF MFGU DPNQMFUFMZ PQFO "OZ

device used or erection in the feld that preventsull openings on ends o horizontal rails andvertical legs should be galvanized separately andattached ater galvanizing.

igure 12 ent holes should be visible on the outside of

DQ\SLSHDVVHPEO\WRSURYLGHLQWHUQDOYHQWYHULFDWLRQ

Figure 13 illustrates an acceptable alternative i ull internalIPMFTUIFGVMM*%PGUIFQJQFBSFOPUJODPSQPSBUFEJOUPthe design o the handrail.

&BDIFYUFSOBMWFOUIPMFNVTUCFBTDMPTFUPUIF

XFMETBTQPTTJCMFBOENVTUCFPGUIF*%o the pipe, but not less than 3/8-inch (10 mm)in diameter. Te two holes at each end and ateach intersection must be 180 apart and inthe proper location as shown.

7FOUIPMFTJOFOETFDUJPOTPSJOTJNJMBSTFDUJPOTmust be 1/2-inch (13 mm) in diameter.

&OET TIPVME CF MFGU DPNQMFUFMZ PQFO "OZdevice used or erection in the feld that preventsull openings on ends o horizontal rails and

vertical legs should be galvanized separately andattached ater galvanizing.

igure 13 xternal vent holes should be visible on the

outside of pipe assemblies

1

2

1

1

1

1

2

2

2

2

2

3

3

4

4

4

4

1

1

1

1

1

1

2

2

3

3

3

3

1

1

1

1

2

2

2

2

2

3

3

4

4

4

4

1

2

3

4

2

2

2

1

1

1

1

1

1

13

3

3

3

3


15/28

ectangular ube russ (Figure 14

Vertical Sections)PMFMPDBUJPOTGPSUIFWFSUJDBMNFNCFSTTIPVMECFBTshown in Figure 14on&YBNQMFT"BOE#

&BDIWFSUJDBMNFNCFSTIPVMEIBWFUXPIPMFTBUFBDIFOE180 apart in line with the horizontal members. Te sizeo the holes preerably should be equal, and the combined

area o the two holes at either end o the verticals shouldbe at least 30% o the cross-sectional area.

End Plates - Horizontal

1. Te most desirable abrication iscompletely open.

2 From Figure 14JG)8wDNPSlarger, the area o the hole, plus clips, shouldFRVBMPGUIFBSFBPGUIFUVCF)Y8

t*G)8MFTTUIBOwDNCVUmore than 16 (41 cm), the area o thehole, plus clips, should equal 30% othe area o the tube.

t*G)8MFTTUIBOwDNCVUmore than 8 (20 cm), the area o thehole, plus clips, should equal 40% othe area o the tube.

t*G)8MFTTUIBOwDNMFBWFit open.

LSH7UXVVFPDUJHU Figure 15

Vertical Sections)PMFMPDBUJPOTGPSUIFWFSUJDBMNFNCFSTTIPVMECFBTTIPXOJO&YBNQMFT"BOE#JOFigure 15.

&BDIWFSUJDBMNFNCFSTIPVMEIBWFUXPIPMFTBUFBDIFOEand 180 apart in line with the horizontal members asindicated by the arrows. Te size o the holes preerablyshould be equal and the combined area o the two holes

BUFJUIFSFOEPGUIFWFSUJDBMT"SFBT$BOE%PS"SFBT&and F) should be at least 30% o the cross-sectional area.

End Plates - Horizontal

1. Te most desirable abrication is completelyopen with the same hole diameter as thetubes inner diameter.

&RVBM TVCTUJUVUFTXPVME IBWF PQFOJOHT BTshown and would be at least 30% o thearea o the inside diameter.

igure 14 oles at either end of the rectangular tube

trusses should be completely open

igure 15 enting and draining holes should be the same

size as the tubing or one of these four possible alternative

1

2

1

2

1

2

A B

E

C C C

A B



16/28

LSH&ROXPQVLSH*LUGHUV6WUHHWLJKW

ransmission oles (Figure 16

8JUICBTFQMBUFTBOEXJUIPSXJUIPVUDBQQMBUFTLocation o Openings

1. Te most desirable abrication is to have the endcompletely open, with the same diameter as thesection top and bottom.

2. Tis is an equal substitute i the ull opening isnot allowed.



5. Tis must be used when no holes are allowed in thecap- or base-plate: two hal-circles 180 apart andat opposite ends o the pole. igure 16 ipe columns pipe girders street

light poles and transmission poles

Dimensions (Figure 16)0QFOJOHTBUFBDIFOENVTUCFBUMFBTUPGUIF*%BSFBPGUIFQJQF

PSQJQFUISFFJODIFTBOEHSFBUFSBOEPGUIF*%BSFBGPSQJQFNBMMFSUIBOwDN"MMPXPGUIFBSFBPGUIF*%GPSIPMFizes at each end.

&OEDPNQMFUFMZPQFO4MPU"JODINN$FOUFSIPMF#JODIFT

(7.6 cm) in diameter

)BMGDJSDMF$JODIDNSBEJVTFYBNQMFPG

sizes or a 6 inch (15 cm) diameter section)0WBMPQFOJOHJODIDNSBEJVT)BMGDJSDMF%JODIDNSBEJVT

%R[6HFWLRQVFigure 17

Figure 17shows the location o holes and clipped corners, whichNVTU CF VTI 6TJOH UIF GPMMPXJOH GPSNVMBT able 1 showsypical sizes o holes or square box sections only. For rectangularection, calculate the required area and check with your galvanizeror positioning o openings.

Internal Gussets space at a minimum o 36 inches (91 cm)Box Sectionst)8wDNPSMBSHFSUIFBSFBPGUIFIPMFQMVT

clips, should equal 25% o the cross-sectional area o theCPY)Y8

t)8MFTTUIBOwDNCVUHSFBUFSUIBOw(40.6 cm), the area o the hole, plus clips, should equal30% o the cross-sectional area o the box.

t)8MFTTUIBOwDNCVUHSFBUFSUIBOPSequal to 8 (20 cm), the area o the hole, plus clips,should equal 40% o the cross-sectional area o the box.

t)8VOEFSwDNMFBWFDPNQMFUFMZPQFOOPend-plate or internal gusset.

igure 1 Box sections

Box Size

( + )

48 (122 cm)36 (19 cm)

32 (81.3 cm)

28 (1 cm)

24 (61 cm)

2 (5.8 cm)

16 (4.6 cm)

12 (3.5 cm)

Holes A-Dia.

8 (2 cm)6 (15 cm)

6 (15 cm)

6 (15 cm)

5 (12. cm)

4 (1.2 cm)

4 (1.2 cm)

3 (.6 cm)

able 1

1 2 3 4

1

2

3

4

1

2

3

4

A C

B

A


17/28

7DSHUHG6LJQDO$UPFigure 18

FTNBMMFOEi"wTIPVMECFDPNQMFUFMZPQFOPole Plate End1. Te most desirable abrication is to have the end

completely open.2. For acceptable alternatives, the hal-circles, slots, andSPVOEIPMFTNVTUFRVBMPGUIFBSFBPGUIF*%o the pole end o the tapered arm or 3 (7.6 cm)BOEMBSHFS*%TFPQFOJOHNVTUFRVBMPGUIF

BSFBPGUIFQPMFFOEPGUIFUBQFSFEBSNJGUIF*%JTless than 3 (7.6 cm).

*OUFSOBMHVTTFUQMBUFT BOEFOEBOHFTTIPVME BMTPCFprovided with vent and drainage holes. In circularhollow shapes, the holes should be located diametricallyopposite each other at opposite ends o the member.

In rectangular hollow shapes, the our corners o theinternal gusset-plates should be cropped. Internalgusset-plates in all large hollow sections should beprovided with an additional opening at the center.8IFSF UIFSF BSF BOHFT PS FOEQMBUFT JU JT NPSF

igure 18 apered - signal arm

FDPOPNJDBM UP MPDBUF IPMFT JO UIF BOHFT PS QMBUFTrather than in the section.

roper enting rainage

of nclosed emi-nclosed

abrications

anks and enclosed vessels should be designed toBMMPXDMFBOJOHTPMVUJPOTVYFTBOENPMUFO[JODUP

FOUFSBU UIFCPUUPNBOEBJSUPPXVQXBSEUISPVHIthe enclosed space and out through an opening at thehighest point. Tis prevents air rom being trapped asthe article is immersed (Figure 19). Te design mustalso provide or complete drainage o both interiorand exterior details during withdrawal. Te locationand size o fll and drain holes are important. As ageneral rule, the bigger the hole the better the air and[JODPX

8IFO CPUI JOUFSOBM BOE FYUFSOBM TVSGBDFT BSF UP CF

galvanized, at least one fll/drain hole and one venthole must be provided. Te fll/drain hole shouldbe as large as the design will allow, but at least 3 indiameter or each cubic yard (10 cm in diameter oreach cubic meter) o volume. Te minimum diameterJT w DN 1SPWJEF WFOU IPMFT PG UIF TBNF TJ[Fdiagonally opposite the fll/drain hole which allows theair to escape.

igure 19 enting of enclosed fabrications

ent diagonally

RSSRVLWHOOKROH

&URSSHGLQWHUQDOEDIH

(top and bottom)

1 2

1

2



18/28

In tanks, internal baes should be cropped on the top andbottoms or provided with suitable drainage holes to permitUIFGSFFPXPGNPMUFO[JOD.BOIPMFTIBOEIPMFTBOEPQFOJOHTTIPVMECFOJTIFEVTIJOTJEFUPQSFWFOUUSBQQJOHexcess zinc (Figures 18-20). Openings must be placed so theVYPOUIFWFTTFMDBOPBUUPUIFTVSGBDFPGUIFCBUIFTFopenings also prevent air-pocket ormations that may keepsolutions rom completely cleaning the inside o the vessel.

Items such as vessels or heat exchangers galvanized on theoutside only must have snorkel tubes, or extended vent pipes.Tese openings provide an air exit rom the vessel above thelevel o molten zinc in the galvanizing kettle (Figure 21).Consult your galvanizer beore using these temporary fttings,because special equipment is needed.

Communication with your galvanizer, including review othe drawings o enclosed or partially enclosed vessels beoreabrication, is critical. Galvanizers may recommend changesthat would provide a better galvanized product, and the least

expensive time to make any changes that may be warranted isbeore abrication.

recautions for verlapping

Contacting urfaces

8IFOEFTJHOJOHBSUJDMFTUPCFHBMWBOJ[FEBGUFSGBCSJDBUJPOit is best to avoid narrow gaps between plates, overlappingsuraces, back-to-back angles, and channels, wheneverpossible (Figure 22).

igure 18 enting of tanks and vessels

igure 19 mproper venting

igure 2 ank

,QWHUQDOEDIHV

cropped top and bottom

ent hole

ill/drain hole

igure 21 ank

ent pipes connect

interior to the

atmosphere

langes should be

QLVKHGXVKLQVLGH

Paul W


19/28

8IFOPWFSMBQQJOHPGDPOUBDUJOHTVSGBDFTDBOOPUCFBWPJEFEand the gap is 3/32-inch (2.5 mm) or less, all edges should becompletely sealed by welding. Te viscosity o the zinc keeps itrom entering any space tighter than 3/32-inch (2.5 mm). I thereis an opening, less viscous cleaning solutions will enter but zinc willnot. rapped solutions may cause iron oxide to weep out o thejoint later on.

igure 22 verlapping urfaces

Additional challenges resulting from tightlyoverlapping surfaces include

1. Cleaning solutions that may beWUDSSHGZLOODVKWRVWHDPZKHQWKH

part is immersed in the galvanizing

EDWK7KLVVWHDPFDQZDVKWKHX[RII

of the part near the gap causing bare

areas adjacent to the lap joint.

2. Cleaning solution salts can be

retained in these tight areas due to

the impossibility of adequate rinsing.

he galvanized coating may be ofgood quality in the adjacent area but

humidity encountered weeks or even

months later may wet these salts. his

will cause unsightly rust staining to

seep out onto the galvanized coating.

3. Cleaning solutions will not effectively

remove oils and greases trapped

between surfaces in close contact.

Any residual oil and grease will

partially volatilize at the galvanizing

temperature. his will result in an

unsatisfactory zinc coating in theimmediate area of the lap joint.

ailure to seal weld small spaces may result

in iron oxide weeping and staining

It is important to contact your galvanizer beore constructing anypiece that will include overlapping suraces. Te trade-o betweena completely sealed weld joint that may undergo expansion andcracking when subjected to galvanizing temperatures and a skip-welded joint that may experience weepage and staining laterbecomes a very dicult choice. Your galvanizers experience can bevery benefcial to assist you in making this decision.



20/28

8IFOBXFMEKPJOUJTDPNQMFUFMZTFBMFEUIFSFNVTUCFOP

weld imperection or pinholes. Te penetration o moisturento the sealed cavity could cause signifcant saety hazards

during the hot-dip galvanizing process as the sealed airwill greatly expand when the part reaches the galvanizingemperature. Tis gas expansion can cause the molten zinco splash out o the bath and endanger galvanizing workers.

the area o a seal-weld overlap is large, there should be vent holeshrough one or both sides into the lapped area. Tis is to prevent

any moisture that gets in through a pinhole in the weld rombuilding up excessive pressure while in the galvanizing bath. Tisventing becomes more important the greater the area. Consultyour galvanizer or the AGA publication Recommended Details orGalvanized StructuresGPSWFOUTJ[FBOERVBOUJUZ7FOUIPMFTDBObe sealed ater galvanizing. Seal welding is not mandatory butprevents trapped moisture, which can result in internal rustingand weepage.

8IFSFUXPCBSTDPNFUPHFUIFSBUBOBOHMFBHBQPGBUMFBTU3/32-inch (2.5 mm) ater welding must be provided toensure the area is wetted by the molten zinc (Figure 23).An intermittent fllet weld may be used. Tis can be on oneide o the bar only, or where necessary, an intermittent

taggered fllet weld may be employed on both sides so thata pocket is not ormed. Tis type o welding, however, maynot be suitable or load-bearing members.

:HOGLQJURFHGXUHV:HOGLQJ

lux emoval

8IFOXFMEFE JUFNT BSF HBMWBOJ[FE UIF DMFBOMJOFTT PG UIFweld area and the metallic composition o the weld itselOVFODFUIFHBMWBOJ[FEDPBUJOHTDIBSBDUFSJTUJDT(BMWBOJ[FEmaterials may be easily and satisactorily welded by all

igure 23 3/32- inch

(2.5 mm) gap after welding

igure 24 Chipping away

ZHOGX[UHVLGXHV

common welding techniques. Te specifc techniquesDBOCFTUCFPCUBJOFEGSPNUIF"NFSJDBO8FMEJOH4PDJFUZ(www.aws.org or 800-443-9353) or your weldingequipment supplier. Additional inormation about welding

galvanized steel may be obtained rom the AGA.

everal welding processes and techniques have beenfound to be successful for items to be galvanized

,Q ZHOGLQJ DQ XQFRDWHG HOHFWURGH VKRXOG EH

XVHGZKHQ SRVVLEOHWR SUHYHQW X[ GHSRVLWV RQ

the steel or product.

:HOGLQJX[UHVLGXHVDUHFKHPLFDOO\LQHUWLQWKH

pickling solutions commonly used by galvanizers;

therefore their existence will produce rough

surfaces and coating voids. f a coated electrode

LVXVHGDOOZHOGLQJX[UHVLGXHVPXVWEHUHPRYHG

by wire brushing chipping grinding pneumatic

needle gun or abrasive blast cleaning (Figure 24).

:HOGLQJSURFHVVHVVXFKDVPHWDOLQHUWJDV0,*

WXQJVWHQLQHUWJDV7,*RUFDUERQGLR[LGH&2)

shielded are recommended since they essentially

produce no slag. owever there can still be small

X[OLNHUHVLGXHVWKDWQHHGWREHFKLSSHGRII

,QWKHFDVHRIKHDY\ZHOGPHQWVDVXEPHUJHGDUF

method is recommended.

,I QRQH RI WKHVH ZHOGLQJ PHWKRGV LV DYDLODEOH

VHOHFW D FRDWHG URG VSHFLFDOO\ GHVLJQHG IRU

self-slagging as recommended by welding

equipment suppliers.

&KRRVHDZHOGLQJURGSURYLGLQJDGHSRVLWHGZHOG

composition as close as possible to the parent

metal. he composition and compatibility will yield

a more uniform galvanized coating appearance.

8FMEJOHSPETIJHI JOTJMJDPONBZDBVTFFYDFTTJWFMZUIJDLand/or darkened galvanized coatings to orm over theweld. In smooth products welded together with high-silicon weld rods, the coating over the weld material willbe thicker than the surrounding coating, causing a bumpin an otherwise smooth product. A very low-silicon, rodshould be used.

18


21/28

hreaded arts

)PUEJQHBMWBOJ[FEGBTUFOFSTBSFSFDPNNFOEFEGPSVTFXJUIIPUdip galvanized subassemblies and assemblies. Galvanized nuts,bolts, and screws in common sizes are readily available romcommercial suppliers. Bolted assemblies should be sent to thegalvanizer in a disassembled condition. Nuts, bolts, or studsto be galvanized also should be supplied disassembled.

Because hot-dip galvanizing is a coating o corrosion-inhibiting,highly abrasion-resistant zinc on bare steel, the original steelCFDPNFTTMJHIUMZUIJDLFS8IFOUBMLJOHBCPVUUBQQFEIPMFTBOEasteners, the increased thickness is important.

Bolts are completely galvanized, but internal threadson nuts must be tapped oversize ater galvanizing toBDDPNNPEBUF UIF JODSFBTFE EJBNFUFS PG UIF CPMUT 8IJMFchasing or retapping the nuts ater galvanizing results in anuncoated emale thread, the zinc coating on the engagedmale thread will protect both components rom corrosion.

For economy, nuts are usually galvanized as blanks andthe threads tapped oversize ater galvanizing (Figure 25).

o remove excess zinc and produce smoother coatings, smallparts, including asteners, are centriuged in special equipmentwhen they are removed rom the galvanizing bath. Items toolong or too large to centriuge, such as long threaded rods,may be brushed while hot to remove any excess zinc rom thethreads. Studs welded to assemblies may have to be cleanedater the assembly has cooled. Tis requires reheating with anacetylene torch and brushing to remove excess zinc. Alternativesto welded studs should be considered when possible.

Masking to prevent galvanizing threads on pipe or fttings isvery dicult. Te recommended practice is to clean and tapater galvanizing. Anchoring devices (such as threaded rodsand anchor bolts) sometimes are specifed to be galvanizedin the threaded areas only or in the areas to be exposed aboveground. Tis can be more expensive than galvanizing thecomplete unit because o the additional handling required.Complete galvanizing can be specifed or items to beanchored in concrete. Research has proven the high bond-strength and perormance o galvanized steel in concrete.

apped through-holes mustbe retapped oversize atergalvanizing i they are tocontain a galvanized bolt aterassembly. apping o all holesater galvanizing is recommendedto eliminate double-tappingcosts and the possibility o cross-threading. Oversizing holes accordingto American Institute o Steel Construction

(AISC) guidelines is usually sucient orclearance holes to account or the zinc coatings thick

able 2 shows the recommended overtapping or nutsinterior threads as detailed in ASM A 563, SpecifcatioCarbon and Alloy Steel Nuts. On threads over 1 1/2-in(38 mm) it is oten more practical, i design strength allto have the male thread cut 0.031-inches (0.8 mm) undebeore galvanizing so a standard tap can be used on the n

igure 25 vertapped nut

ncrease

tolerance

Overtapping

uidelines for uts &

nterior Threads

ominal ut

ize (inches)

and itch

.25-2

.312-18

.35-16

.43-14

.5-12

.562-12.625-11

.5-1

.85-9

1.-8

1.125-

1.25-8

1.25-

1.35-8

1.35-6

1.5-8

1.5-6

1.5-5

2.-4.5

2.5-4.52.5-4.5

2.5-4

3.-4

3.25-4

3.5-4

3.5-4

3.5-4

4.-4

or metric overtapping

allowance see AM A 563M

section

able 2

iametrical

Allowance

(inches)

.16

.1

.1

.18

.18

.2.22

.24

.24

.24

.24

.24

.2

.2

.2

.2

.5

.5

.5

.5.5

.5

.5

.5

.5

.5

.5

.5



22/28

)JOHFTTIPVMECFHBMWBOJ[FETFQBSBUFMZBOEBTTFNCMFEater galvanizing. All hinges to be galvanized shouldbe o the loose-pin type. Beore galvanizing, anyadjacent edges should be ground to give at least1/32-inch (0.8 mm) clearance (Figure 27). Te pinholes can be cleared o excess zinc during assembly.Ater hinges are galvanized, it is recommended anundersized pin be used to compensate or the zincpicked up during galvanizing. I desired, the pin holesin the hinges may be reamed 1/32-inch (0.8 mm)

ater galvanizing to permit the use o regular-sizepins. On hinges, all adjacent suraces must be ground1/32-inch (0.8 mm) on both pieces to allow orthickness increases. Grinding both pieces is necessary.

At times, moving parts must be reheated in orderor them to work reely. Although heating may causediscoloration o the galvanized coating near thereheated area, this discoloration does not aect thecorrosion protection o the galvanized surace.

Manuacturers o threaded parts recognize special proceduresmust be ollowed in their plants when certain items areto be galvanized. Following are some examples:

t-PXDBSCPOCBSTBSFSFDPNNFOEFETJODFIJHIcarbon or high silicon cause a heavier, roughergalvanized coating on the threads.

t)PUGPSNFEIFBEJOHPSCFOEJOHSFRVJSFTcleaning at the manuacturing plant to remove

scale beore threading. Otherwise, over-picklingo threads will result during scale removal.

t4IBSQNBOVGBDUVSJOHUPPMTBSFNBOEBUPSZ3BHHFEand torn threads open up in the pickling andHBMWBOJ[JOHQSPDFTTFT8PSOUPPMTBMTPJODSFBTFbolt diameters. Frequent checking is necessary onlong runs.

t4UBOEBSETJ[FEUISFBETBSFDVUPOUIFCPMUwhile standard sized nuts are retapped oversizeater galvanizing.

oving arts

8IFOBHBMWBOJ[FEBTTFNCMZ JODPSQPSBUFTNPWJOHQBSUT(such as drop-handles, shackles, and shats), a radialclearance o not less than 1/16-inch (1.5 mm) mustbe allowed to ensure ull reedom o movement aterthe addition o zinc during galvanizing (Figure 26).8IFOFWFS QPTTJCMF XPSL TIPVME CF EFTJHOFE TP UIBUhinges can be bolted to rames, covers, bodies, and otheritems ater galvanizing.

igure 26 haft

igure 2 inge

20


23/28

Additional esign Considerations

0DVNLQJ

%VSJOH UIF HBMWBOJ[JOH QSPDFTT BMM TVSGBDFT BSF DMFBOFE

and coated with zinc. For some purposes, intentionallyungalvanized areas are required. Masking, treating a portiono the steel surace so the area remains ungalvanized, maybe perormed to accomplish this. Masking is not an exactscience; thus, additional work may still be required toremove unwanted zinc. In most cases, it may be easier togrind o the zinc coating ater galvanizing than to the maskthe material.

Tere are our major categories o masking materials:

t"DJESFTJTUBOUIJHIUFNQFSBUVSFUBQFT

t8BUFSCBTFEQBTUFTBOEQBJOUPOGPSNVMBUJPOT

t3FTJOCBTFEIJHIUFNQFSBUVSFQBJOUT

t)JHIUFNQFSBUVSFHSFBTFTBOEUISFBEDPNQPVOET

Te AGA is conducting a masking study to identiy othercommon products that can be used eectively in the hot-dipgalvanizing process. Masking can also be done at the abricatorsshop to correctly locate the area to be ree o coating.

0DUNLQJIRUGHQWLFDWLRQ

Identifcation markings on abricated items should becareully prepared beore galvanizing so they will be legibleater galvanizing, but not disrupt the zinc coatings integrity.Cleaning solutions used in the galvanizing process willnot remove oil-based paints, crayon markers or oil-basedmarkers, so these products should not be used or applyingaddresses, shipping instructions, or job numbers. I theseproducts are used, ungalvanized area may result.

%FUBDIBCMFNFUBMUBHTPSXBUFSTPMVCMFNBSLFSTTIPVMEbe specifed or temporary identifcation. Alternatively,barcode tags are manuactured to survive the hot-dipgalvanizing process and easily maintain identifcation.

8IFSF QFSNBOFOU JEFOUJDBUJPO JT OFFEFE UIFSFare three suitable alternatives or marking steelGBCSJDBUJPOT UP CF IPUEJQ HBMWBOJ[FE &BDI FOBCMFT

items to be rapidly identifed ater galvanizing and atthe job site (Figures 28 & 29).

Stamp the surace o the item using die-cut deep stencilsor a series o center punch-marks. Tese marks should beplaced in a standard position on each o the members,preerably toward the center. Tey should be a minimumo 1/2-inch (13 mm) high and 1/32-inch (0.8 mm) deep toensure readability ater galvanizing. Tis method should notbe used to mark racture-critical members.

A series o weld beads may also be used to mark letters ornumbers directly onto the abrication. It is essential thatBMMXFMEJOHVYCFSFNPWFE JOPSEFS UPBDIJFWFBRVBMJUZgalvanized coating (Figure 29).

igure 29 A series of weld beads may be used to

identify the fabrication

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tamped/elded tag

eal-welded to Member

tamped/elded tag

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24/28

%FFQTUFODJMJOHBTUFFMUBHNJOJNVNHBVHFBOESNMZBYJOHJUUPUIFGBCSJDBUJPOXJUIBNJOJNVNHBVHFTUFFMwire is another option or identifcation (Figure 30). Te tagshould be wired loosely to the work so that the area beneaththe wire can be galvanized and the wire will not reeze to thework when the molten zinc solidifes. I desired, tags may beseal-welded directly to the material.

ost-alvanizing ConsiderationsOnce the abrication has been successully galvanized, thereare a ew additional considerations to take into accountregarding storage and use. Tese best practices will ensureyour galvanized project will provide maintenance-reecorrosion protection as anticipated.

torage

Zinc, like all metals, begins to corrode naturally whenFYQPTFE UP UIF BUNPTQIFSF )PXFWFS [JOD DPSSPTJPOproducts actually orm a tenacious, abrasion-resistant patinawhich helps to provide hot-dip galvanizing with its longservice lie. Te ormation o this patina depends on thegalvanized coating being exposed to reely circulating air.Stacking galvanized articles closely together, or nesting, orextended periods o time, thereby limiting access to reelycirculating air, can lead to the ormation o a white powderyproduct know as wet storage stain.

o minimize the possibility of wet storage stain

these storage guidelines should be followed

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pieces and avoid nested stacking

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with strip spacers (poplar ash spruce); and during

shipping if there is the likelihood of condensation

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at in-transit loading points where it may be

exposed to rain mist condensation or snow

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and stored in containers and include a

dehumidifying agent in the sealed containers

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well-ventilated conditions away from doorways

open to the environment

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minimum #9 gauge steel wire

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spacers to avoid wet storage stain

oles with wet storage stain

22


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8FUTUPSBHFTUBJOJOHJTPGUFOTVQFSDJBMEFTQJUFUIFQPTTJCMFpresence o a bulky white product. In the vast majority ocases, wet storage stain does not indicate serious degradationo the zinc coating, nor does it necessarily imply any likelyreduction in the products service lie. I wet storage staindoes orm, the objects should be arranged so that theirsuraces dry rapidly. Once dry, most stains can be easilyremoved by brushing with a sti bristle (not wire) brush.I the aected area will not be ully exposed in service, ori it will be subject to an extremely humid environment,

even superfcial white flms should be removed with a sti-bristle brush. Tis allows or the successul ormation ogalvanized coatings protective zinc carbonate patina.

Cleaning alvanized teel

Once in service, galvanized suraces may need to becleaned to remove grati or other contaminants. Tere area number o products that can be used to successully cleanhot-dip galvanized steel without damaging the coating.Contact the AGA or more details.

ollow these easy steps to clean the surface

1. se suitable personnel protective equipment

2. Apply cleaning product

3. et sit for appropriate time

4. ipe off with clean cloth

issimilar etals

8IFO [JOD DPNFT JOUP DPOUBDUXJUI BOPUIFSNFUBM VOEFSatmospheric or aqueous conditions, the potential or corrosionthrough a bimetallic couple exists. Te extent o corrosion willdepend upon the position o the other metal relative to zinc inthe galvanic series (Figure 31), the relative surace areas o thetwo metals in contact, and the conductivity o the electrolyteon the surace o the two metals.

6OEFS BUNPTQIFSJD DPOEJUJPOT PG NPEFSBUF UP NJMEhumidity, contact between a galvanized surace andaluminum or stainless steel is unlikely to cause substantialHBMWBOJDDPSSPTJPO)PXFWFSVOEFSWFSZIVNJEDPOEJUJPOTthe galvanized surace may require electrical isolationthrough the use o paint or joining compounds. Youshould always consult your galvanizer or the AGA whendesigning a project with galvanized steel in contact withother metals.

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)PUEJQHBMWBOJ[FETUFFMQSPWJEFTVOJOUFSSVQUFEDPSSPTJPOQSPUFDUJPO JOBXJEF WBSJFUZPG UFNQFSBUVSFT )PXFWFSsome extreme temperatures can aect the coating. Coldtemperatures have little aect on the galvanized coating.On the other hand, constant exposure to temperaturesabove 390 F (200 C) will cause the coating to separate andis not recommended. Short times at temperatures above390 F do not eect the galvanized coating.

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Corroded End(Anodic or less noble)

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2American alvanizers Association


26/28

American ociety for esting and Materials

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AM A 143 ractice for afeguarding against mbrittlement of ot-ip

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ardware urfaces for ainting

AM 36 ractice for Measuring Coating hickness by Magnetic-ield or

ddy-Current (lectromagnetic) est Methods

Canadian tandards Association

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urther eading elated Materials

Hot-Dip Galvanizing for Sustainable Design

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Hot-Dip Galvanizing for Corrosion Protection


Recommended Details for Galvanized Structures


The Inspection of Hot-Dip Galvanized Steel Products


Hot-Dip Galvanized Fasteners


Welding & Hot-Dip Galvanizing


24


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American alvanizers Assocation

6881 S olly Circle Suite 18

Centennial CO 8112

8.468.7732

[email protected]

www.galvanizeit.org

Documents

AGA Design Guide