Valm Coat Galvtech 102804

8/22/2019 Valm Coat Galvtech 102804

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galvanize


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alvanized to exceed your expectations.

The Lead ing Galvan i zer

As a full-service coatings company, Valmont

Coatings provides quality surface finishes

that extend the service life and improve the

appearance of metal products throughout

the country. Our processes and transportation

capacities are designed to efficiently handle

steel products of all shapes and sizes, for

customers anywhere in the country.

Valmont Coatings is the market and technical leader in hot dip galvanizing.We are one of the largest custom galvanizers in North America, serving allsteel fabrication markets from coast to coast. Valmont Coatings is a membeof the American Galvanizers Association.

I ntroduct ion

The size of products that can be hot dip

galvanized is determined by the size of

the zinc kettles, the tanks in the cleaning

line, the crane capacities, or the building

structure clearances within a particular

galvanizing plant.

The most economical and highest quality

galvanizing is achieved when steel products

are sized to enable the entire product to

be totally immersed in the molten zinc in

a single dip.

When needs dictate that the product to

be galvanized must be longer or deeper

than the galvanizers kettle, it can often be

galvanized by means of the double dipping

procedure. With this method, 50% or more

of the surface of the product is immersed in

the molten zinc. When the galvanizing of that

portion is completed, the product is turned

over and the remaining uncoated portion

is lowered into the zinc and galvanized.

This section will guide the prospective

user of Valmont Coatings service to

determine common size and weight

limits for products that are single-ordouble-dipped within our plants.

We urge fabricators, engineers and

architects to consult with us if the product

under consideration is slightly larger than

the dimensions cited in this brochure.

In some situations, depending upon the

design of the product, certain special

procedures can be used to satisfy

greater requirements.

Fac i l i t i e s and Process

Valmont Coatings uses galvanizing kettles

that typically are the following sizes:

At the beginning of the process, products

are batched into bundles, trays or racks

to be handled in the most effective manner

through the cleaning line. At this stage,

each product is examined to determine the

presence of adequate details for venting

and draining of fluids during cleaning and

galvanizing, and to assure that, when

necessary, the product is provided with

holes or lugs for lifting. If additional venting

details or lifting holes/lugs are required, the

customer is notified and arrangements are

made to install them.

After batching, the products are passed

through the stages of the cleaning and

galvanizing line, illustrated in Figure 1.

This schematic applies to products whose

coating must meet the requirements of

ASTM Specification A 123.

When parts are required to have excess

zinc removed by centrifuging or brushing,

the stages shown in Figure 2 are applicable.

Products are galvanized in this manner

to conform to the requirements of ASTM

Specification A 153.

Caustic The caustic tank contains

heated water with caustic soda and

detergent additives. Oils, soil and soluble

paint markings are removed from products

during immersion at this stage.

Rinse A tank containing plain wate

used to remove residues of the caust

Pickle A bath of heated dilute sulfu

acid solution removes rust and mill sc

from the products.

Rinse Another tank containing plain

is used to remove residues from pickl

Flux Zinc ammonium chloride in sol

provides additional cleaning of the pro

being dipped. During galvanizing, the

of flux on the products improves wett

between the steel and the molten zinc

Re-fixturing Depending upon the p

uct and/or type of batching used duri

cleaning, some products are re-fixture

or re-batched, for better processing

through the molten zinc bath.

Galvanizing The fluxed, possibly re-

tured, product is taken to one of the z

kettles. Each kettle is provided with a f

black blanket of zinc ammonium chlor

flux which floats on the surface of the

ten zinc. The products are lowered thr

the flux blanket en route to the molten

below and, in so doing, receive one fin

cleaning. Products remain in the molte

until they reach the approximately +83

molten zinc temperature.

Centrifuging or Brushing (For ASTM

153 Only) When the perforated bas

containing the product is removed fro

the molten zinc, it is transferred imme

ately to the centrifuge where excess z

is spun away.

Process and Sizing Guide For Hot Dip Galvanizing


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Products that are too large to be centri-

fuged, but are still in need of removal of

excess zinc, are subjected to brushing of

the critical areas before the zinc solidifies.

Quench After galvanizing and centrifuging

or brushing (when applicable), the product

is immersed in a plain water quench to

retain as much bright zinc surface as

possible and to reduce the time required

for handling.

Inspection Products are visually checked

for coating integrity and measured to verify

that coating thickness meets or exceeds

ASTM Standards.

S ize L im i ts S ing le D i p

Lifting Capacity: 10,000 lbs.

Height

26 or 52 kettle length

Product length

26 Foot Kettle Maximum product

dimensions: 25-8 long x 4-4 wide x

6-0 high.



5-0 high.

Size L im its Double Dip

Lifting Capacity: 10,000 lbs.

1. Double dip for height

Height

Kettle length

Product length


dimensions: 24-0 long x width and height,

from this table:

Width Maximum height

Up to 9 12-0

+9 to 12 11-7

+12 to 24 10-5

+24 to 52 10-4



10-0 high.

2. Double dip for length

Kettle length

Productlength

height

Maximum product dimensions: 4 x 4 wide

x length and height from table below:

Maximum

Maximum length using

length using all dip stages

Height all dip stages except caustic*

Up to 6 61-10 72-0

+6 to 12 62-9 72-0

+12 to 18 62-8 72-0

v+24 to 30 62-7 71-9

+30 to 36 62-6 67-0

+36 to 39 62-6 64-11

+39 to 42 See note 1 62-8

+42 to 48 See note 1 58-4

Note 1: Items 39 through 48 in height are

too large for caustic double dipping and

can only be processed if they are given

SP-6 Commercial Blast before supplying

to Valmont.

*Products can be galvanized to the lengths

given in this column when steel is cleaned

to SP-6 Commercial Blast before sup-plying to Valmont. Such cleaning enables

bypass of size restriction imposed at the

caustic tank.

Limited by building structure clearance.

S ize L im i ts C entr i f

Maximum product dimensions:

Rounds: 18 long x 4 diameter

Plates: 6 x 6 x 1 thick

Angles: 5 x 5 x 1/2 thick x 6 long

Consult with Valmont Coatings if the

product under consideration is slightl

larger than the dimensions given in th

brochure. In some situations, depend

on the design of the product, certain

special procedures can be used to

satisfy greater requirements.

Caustic Rinse Pickle Rinse Flux Solution Zinc Bath Quench Inspectio

Caustic Rinse Pickle Rinse Flux Solution Transfer to Basket Zinc Bath Centrifuge(or Brush)

Quench Inspectio

Figure 1: Process for ASTM A 123

FIGURE 2: Process for ASTM A 153


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Introduction and Purpose

The galvanizing of products that are made

from tube or pipe requires special attention

by the fabricator and the galvanizer. Instal-

lation of suitably sized holes in strategic

locations on the product is essential to

assure the correct galvanizing of all internal

surfaces. The holes, so placed in the prod-

uct, serve several purposes, namely to:

1. Prevent pressure build up and rupture

of the product that could result from

heating of enclosed air and moisture

during partial or full immersion in the

840 F galvanizing bath.

2. Provide for the rapid entry of cleaning

fluids and molten zinc to overcome the

natural buoyancy of hollow objects.

3. Enable air and galvanizers flux to escape

from the last remaining upper corners

of a product at the moment of total

immersion. Elimination of air pockets

allows cleaning fluids and molten zinc

to reach all surfaces to permit complete

internal cleaning and coating. Evacua-

tion of flux eliminates a potentially

corrosive internal condition.

4. Eliminate the entrapment of pockets of

zinc as the product is being withdrawn

from the galvanizing bath. Properly sized

and placed holes avoid large and costly

volumes of zinc from solidifying in

deep recesses.

5. Contribute to the safety of galvanizing

plant personnel.

Holes, placed in products to fulfill the

functions listed, are referred to as

vents and drains* in the galvanizing

industry. Size and location of such holes

are a frequent topic of conversationbetween a galvanizer and t he fabricator.

Conservative recommendations on the

size and location of openings are given

in ASTM A 385, Standard Practice for

Providing High Quality Zinc Coatings

(Hot-Dip). In order to select adequate,

yet economical details for vents and

drains, it is necessary to understand

how the product will be oriented as it

is being lowered into the baths. This is

not something that a fabricator could

reasonably know without prior guidance.

The purpose of this brochure is to

acquaint the fabricator with the principles

that Valmont uses in determining how

to position a work piece for lowering

into the baths, and how this leads to

a determination of where the vents

and drains should be located.

Some examples are given to show

how the principles are applied to

tubular products but, since the type and

configuration of products are so varied,

we are relying on these principles, coupledwith the fabricators knowledge of their

own product, to enable them to determine

where vents and drains are required.

*Holes that are used to drain as a part is

being removed from the bath have earlier

served as fillholes during the immersion

of the part. For purposes of this brochure,

use of the terms fill and drain should

be taken to describe the same hole,

depending upon how it is functioning

at a particular stage of the process.

Pr inc i p l es

1. Product Is Oriented to Maximize

Bath/Kettle Space

Bath width

Product width

Generally, products are set up for galvanizing

so that their smallest dimension parallels

the bath width. Several identical pieces

can often be galvanized side by side at the

same time, thereby utilizing most of the

width of the cleaning bath or zinc kettle.

It is with this orientation that the consider-

ation of vent and drain openings begins.

2. Initial Fill Location Is at Largest

Available End Opening

An opening at, or very near to, a lower end

location of the product is selected as the

initial entry opening to allow cleaning fluids

and molten zinc to flow i nto the interior.

When a product has an opening at each

of its two ends, and one of these openings

is larger than the other, the larger opening

will be chosen as the entry orifice, provided

that it can be situated near the bottom of

the product when suspended by a crane.

3. Final Vent Is at Position

Immersed Last

Good internal galvanizing depends on the

ability of cleaning fluids and molten zinc to

surge through the hollow product from the

entry to the exit point, without compress-

ing any air into pockets in its path. In any

hollow product, the last exit point must be

located at the place where the last portion

of the hollow component submerges into

the bath.

4. Lift Orientation Is Suited to Initial Fill,

Final Vent Locations

Vent

Fill

As the work piece is being lowered into

each of the baths, the natural tendency

of the cleaning fluid and molten zinc is

to push upward through the product.

To enhance this movement and to

encourage a flow, especially along

longitudinal components of the products,each work piece is arranged at a sli ght

angle on the hoisting equipment as shown.

5. Size, Style and Location of Open

Are Adequate

Vent

Fill

Fill

Vent

Fill

For secondary components, as for pr

members, fill holes (F) need to be loca

as close as possible to the point on th

member where the fluids first make co

during immersion. Similarly, vent holes

on secondary members need to be as

close as possible to the point where th

member is finally and completely imm

Other Valmont Coatings recommend

relating to openings are as follows:

Minimum Size of Openi

Requirements for fill and vent opening

vary according to the size of tube or p

being filled, and whether that tube or

is a primary or secondary componen

the overall product. Fill and vent open

for primary members apply when the

members have end closures of any k

The following tables provide guideline

on sizes that Valmont Coatings gene

considers to be minimum.

Pipe and Round Tube

Minimum Fill and

Vent Hole Diameter

Pipe & Tube Primary Seconda

Diameter Member Member

1-14, 1-12 5/8 3/82 7/8 1 2

4 1-5/8 7/8

6 2-3/8 1-14

8 3-14 1-5/8

10 4 2

12 4-5/8 2-3/8

14 5-14 2-5/8

16 6 3

18 7 3 12

20 8 4

Fabricators Guide to Pipe and Tube Galvanizing

In order to select adequate, yet economical detailsfor vents and drains, it is necessary to understandhow the product will be oriented as it is beinglowered into the baths. is is not somethingthat a fabricator could reasonably know without

prior guidance.


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Square or Rectangular Tube

Triangular corner cutouts, rather than round

holes, are suggested for fill or vent open-

ings in end closures on primary members

made of square or rectangular tube. Round

holes, however, remain suitable to be fill

or vent openings in secondary members

made from this type of tube. The following

table lists square-inch units for minimum

opening sizes in primary members, and

hole diameters in inch units for minimum

openings in secondary members.

Minimum Fill and

Vent Hole Size

Tube Cross Primary Secondary

Section* Member Member

(sq. in.) (sq. in.) (inches)

2.25 0.6 124.0 1.0 5/8

9.0 1.25 5/8

16.0 2.75 1

25.0 4.5 1-14

36.0 5.5 1-3/8

49.0 8.0 1-5/8

64.0 11.0 1-7/8

81.0 13.0 2

100.0 15.0 2-14

*Interior cross section, square or rectangular tube.

Qual i ty o f Open ing

The evenness of the edge of an opening

plays a significant part in helping Valmont

Coatings achieve a good looking galva-

nized coating around it. Regular openings

allow a smooth spill of molten zinc upon

withdrawal from the bath. Irregular, ragged

edge openings cause molten zinc to splat-

ter as it pours and should be avoided.

Good Avoid

Locat ion o f Open ings

Openings are best located where they

will help to fill, vent and drain the tubes

most rapidly. Their location on individual

components must be related to the listing

direction of the overall assembly.

(a) In Primary Members

Fill (Near end)

Lift Lift

Lift Lift

Vent (Far end)

Fill (Near end)

Vent (Far end)

Round single Square or rectangle single

Round assembly Square or rectangle assembly

(b) In Secondary Members

Perpendicular member

1/2 maximum

6. Product Filled Slowly, Gradually

from End to End

Slow immersion allows the bath and the

product to adjust for their very different

initial temperatures. Filling from end to

end allows flux on the interior surfaces

to be flushed out of the product.

7. Product Is Drained Through Original

Fill Holes

The sloped orientation of the work piece

on the lifting equipment facilitates drainage.

Further Ass i s tance

Valmont Coatings will provide help to

customers, upon request, to establish the

size and location of vent and drain holes

during the fabrication of an order.

If Valmont Coatings technicians determine

additional vent and drain fabrication is

necessary once a product is in the Valmont

plant, we will noti fy the customer, provide

costs for appropriate modifications and

request permission to install or modify

the holes.

Angled member

3/4 maximum

3/8 diameterPrimary fill

1/2 maximum

Dip direction

5/8 diameterPrimary fill

1/2 maximum

3/8 diameterSecondary vent

1/2 maximum

1-1/2 Pipe handrail

1/2 maximum

3/8 diameterSecondary fill


5/8 diameterPrimary vent


1/2 maximum

Pipe Handrail


Two cutouts 1 x 1-1/4 (1.25 sq. in.)Primary vent


3/4 maximum

Open end

3-1

/2

x2

-1/2T

ub

e

2-1/2

x2-1/2Tub

e

Dip direction

Tubular Bracket

Examp les


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Fabricated steel products that are to be

galvanized should have details that would

allow the galvanizers cleaning solutions

and molten zinc to flow freely through the

product at various stages throughout the

hot dip galvanizing process.

When such details are made, they elimi-

nate the formation of air pockets during

dipping. This helps to assure that the steel

is thoroughly cleaned and coated in all

corners. Improperly cleaned areas of steel

will not galvanize.

Details that allow a clear path for the

run-off of molten zinc when steel parts

are being withdrawn from the galvanizers

kettle result in a coating that is more evenly

formed throughout the product. Proper

details prevent unwanted zinc build-ups

which, ultimately, add to the customers

cost, look unsightly, and may interfere

with the fit-up of adjoining parts.

To determine how to avoid pockets and

traps when a product is being hot dip

galvanized, the fabricator must first

understand how a product will be oriented

as it is being lowered into and lifted from

the baths. This is not something that a

fabricator could reasonably be expected to

know without guidance from the galvanizer.

The purpose of this brochure is to acquaint

the fabricator with the principles that

Valmont Coatings uses to: (1) determine

how to position a work piece for lowering

into, and lifting from, the baths, and (2)how this leads to a determination of where

vents and drains should be located. The

focus of this section is on the fabrication

details for products made of open-sided

components.

Examples are provided to show how the

principles are applied to fabrications made

of open-sided components. However, since

the type and configuration of products are

so varied, Valmont Coatings relies on these

principles, coupled with the fabricators

knowledge of their own product, to help

them determine where vents and drains

are required.

Pr inc i p l es

1. Product Is Oriented to Maximize

Bath/Kettle Space

Bath width

Product width

Generally, products are set up for galvaniz-

ing so that their smallest dimension parallels

the bath width. Several identical pieces

can often be galvanized side by side at the

same time, thereby utilizing most of thewidth of the cleaning bath or zinc kettle.

2. Product Support Locations Depend

on Size, Configuration and Number

of Pieces per Lift

Product is set up for galvanizing either by

being placed into a rack, or by suspension

from a harness of wires that is attached

through a suitably placed hole at a corner

location near to the end of the product.

Rack

Use of a rack is preferable when: (1) there

are many identical pieces to be galvanized,

such as warehouse stock angle; (2) these

pieces are generally not more than 4 x 4

in cross-section; and (3) they are no more

than 20 in length. Items galvanized in a

rack do not need to be provided with a

pick-up hold.

Side view of loaded rack

Product

Fabricators Guide to Open Section Galvanizing

The majority of items that are hot dip

galvanized are suspended by wires

attached at one or more pick-up

points on each work piece.

Single Point Pick-Up

In general, Valmont will suspend from

a single corner pick-up point if: (1) the

geometry of the product is reasonably

streamlined along its length; (2) the product

would give minimal drag through molten

zinc as it was being moved along the

length of the kettle; (3) the length and

major cross-section dimension of the

product falls at or below the limits of the

graph given below; and (4) if the minor

cross-section dimension of the product

is not greater than 7.

Examples of products suited to single point pick-up

The graph is intended to provide only a

very approximate guideline as to whether

a product may be supported at a single

pick-up point.

Example: A product with a major cross-

section dimension of 20 and a minor

cross-section dimension of 7 and a

length of 11 will be lifted from a single

pick-up point.

The required pick-up hold size is 3/8

diameter for items weighing less than 100

pounds, and 5/8 diameter for heavier items.

Two Point Pick-Up

Any product for which rack or single point

pick-up is not practical is picked up from

a wire harness through a hole in each of

its two ends.

The required pick-up hold size is 3/8

diameter for items weighing less than 200

pounds, and 5/8 diameter for heavier items.

The product is arranged on the lifting

equipment so that it enters the bath at an

angle. The angular orientation is used to

encourage a flow of molten zinc to move

progressively along each component of

the product from one end to the other.

This provides a more uniform wetting

action between the steel and the zinc,

and better drainage upon withdrawal.

3. Choice of Top or Bottom Side

Is Based on Openness

Determination is made as to which of

two sides of a product will be first to

lowered into the bath. This is particula

significant when the ends (in the case

one point pick-up) or the sides (in the

of two point pick-up) are not the sam

Guidelines to help determine how a p

uct will be hung, based upon its widt

provided in Principle No. 1. It must als

determined which remaining side will

the top, and which will be the bottom

For each submersion of non-symmet

products, Valmont will choose the sid

is most open to be the bottom.

Liquid surface

A table-like stand, for instance, would

lowered legs first.

Product length (Feet)

MajorCrosssectiondimension(Inches)

5

10

20

30

40

50

60

6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

9 8 7


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4. Potential Air Pockets and Zinc

Traps Are Identified

Once it has been determined how a

product is likely to be picked up and

oriented, it is possible to identify places

where air pockets could potentially form

during submersion, and also where molten

zinc could be prevented from draining

during withdrawal.

The illustrations provide examples of

frequent problem areas and the proper

methods to avoid them.


Valmont will provide help to custome

upon request, to establish the size an

location of vent and drain holes durin

fabrication of an order.

If Valmont Coatings technicians deter

additional vent and drain fabrication is

necessary once a product is in the Va

plant, we will notify the customer, pro

costs for appropriate modifications a

request permission to install or modif

the holes.

Detail needed:1/2 diameter hole madeat each corner preventsair pocket formation

Liquid surface

Dip direction

Air pocket

Venting at structural panel point

Detail needed:1/2 diameter hole madeat each corner preventsa trap for galvanizing liquids

Liquid surface

Withdrawal

Trapped liquid

Draining at structural panel point

Detail needed:1/2 diameter hole madein a corner of the web, andas close to the plate aspossible, prevents airpocket formation

Liquid surface

Dip direction

Air pocket

Hanging wire

Venting at base of post

Air pocket

Liquid surface

Dip direction

Hanging wire

1/2 diameter pick-up / vent hole 2 diameter hole forfilling and drainingat the lower rightcorner of the back wall

Venting and draining of enclosure body

Detail needed:1/2 diameter pick-up holein flange, and as close aspossible, also serves as avent to prevent formationof an air pocket. Seeenlarged detail.

Venting and draining of a stand

Construction: Angle legs and braces; sheet or placetop and shelf with brake formed flanges.

Liquid surface Dip direction

Air pocket

Air pocket

Detail needed:

1/2 diameter hole made in the angle anddownturned flange of top prevents airpocket formation. Holes need to be asclose to the top corner as possible.

Detail needed:

1/2 diameter hole made in theangle and downturned flangeof the shelf prevents air pocketformation. Holes need to be asclose to the inside corner of theshelf as possible.

Alternative: 1/2 diameter holesin the top surface of the shelf asclose to the corner as possible.

Detail needed:

1/2 diameter hole made in each angle prevents a trap forgalvanizing liquids. Holes need to be as close to the topsurface of the shelf as possible.

Alternative: 1/2 diameter holes in the topsurface of the shelf as close to thecorner as possible.

Note 1:

1/4gap.Ifno gap,provide1/2diameterholeintheend ofthehorizontalleg ofbraceangle.

Detail needed:

1/2 diameter hole made inthe leg of each angle prevents atrap for galvanizing liquids. Holesneed to be as close to the cornerof the angle and the base plateas possible.

Hanging wiretypically four places

Seenote 1

Seenote 1

Seenote 1

Shelf


8/13


This article describes major causes of

distortion that become evident after hot

dip galvanizing and suggests ways to

reduce the risk.

Considering the volume of products that

are hot dip galvanized, the occurrence of

distortion is quite infrequent. When it does

happen, however, distortion is a serious

concern to the fabricator and galvanizer

alike, involving extra costs and possibly

delays to remedy the problem.

An understanding of the causes of

warpage during galvanizing can lead to

measures that will eliminate or substantially

reduce the problem.

Overv i ew

In many instances, the potential for distor-

tion has been put i nto the product before

its arrival at the galvanizing plant. Distortion

can be due to:

residual stresses induced at the mill dur-

ing rolling of structural sections or plate;

residual stresses created by bending

or welding;

lack of symmetry in simple sections

such as channels or in built up sections;

a combination of thick and thin material

in the same assembly;

assemblies made so large that they

require double dipping to be coated

over their entire surface.

Some causes of distortion can arise at the

galvanizing plant. These can be due to:

poorly selected pick-up points for

handling product through the process;

random laydown of product after

galvanizing, especially of products

leaning against each other or against

other objects, that may establish

a deformed set in the product

during cooling.

The remainder of this article details causes

of distortion that can be controlled by the

fabricator or the galvanizer and describes

preventive measures that can be applied

to each case.

Causes and Prevent ion

Cause: Bending

While a product may have the correct form

in the as fabricated condition, stresses

induced in the product during bending

operations at the fabricating plant may be

released when the product is galvanized.

The galvanizing temperature, 820 to 870

F, is at the low end of the stress relieving

temperature range. Consequently, stresses

induced by bending may be released

during galvanizing with a resultant

change in shape or dimension of the

fabricated product.

Consider the case of a plate section that

has a curve rolled into it so that when

several such sections are joined, they form

a circle. As a result of galvanizing, the plate

would relax to a greater radius than thedimension originally fabricated.

Prevention:

Installation of temporary struts across the

chord of the circle will enable the curved

section to retain its form. The struts would

be structural angles or channels bolted or

welded into position. Their size will be pro-

portional to the size and thickness of the

plate section. The struts should be located

at the quarter points of the height of the

section as shown below.

Control of Distortion in Galvanized Products

1/4 H

H

1/4 H

After galvanizing, it would be necessary

for the fabricator to remove the struts

and repair the area where they had been

joined to the plate.

Valmont would be pleased to assist in

establishing strut and end connection

details based on each particular case.

Cause and Prevention: Welding

There are several actions the fabricator

should take to minimize the potential for

distortion due to the release of stresses

in welds. Those actions are as follows:

avoid over welding;

use as few weld passes as possible;

place welds near the neutral axis;

balance welds around the neutral axis;

use backstep welding;

make weld shrinkage forces work

in the desired direction;

balance shrinkage forces with

opposing forces;

use a well planned, balanced welding

sequence;

remove weld shrinkage forces during

and after welding;

reduce the welding time.

More information on these points and

much additional guidance on minimizing

distortion in weldments is given in the

brochure, Distortion . . . How to Minimize

It With Sound Design Practices and Con-

trolled Welding Procedures, Plus Proven

Methods for Straightening Distorted

Members, written by Omer W. Blodgett,

P.E., and Duane K. Miller, P.E., and

published by Lincoln Electric Company.

Valmont will be pleased to furnish a

complimentary copy upon request.

Cause: Lack of Symmetry in Product

The potential for warpage is greatly

reduced when a product is symmetrical

about its horizontal and vertical neutral

axes. When a symmetrical section such

as a simple I-beam is galvanized, thermal

expansion forces above and below the

neutral axis balance each other and l eave

the beam free of distortion.

However, in the case of unsymmetrical

sections, such as a wide flange beam

with a rectangular structural tube welded

to its top flange, a geometric imbalance

has been created. The wall of the tube is

considerably thinner than the flange of the

beam. Consequently, the tube material will

be thoroughly heated to the temperature

of the galvanizing bath, while the bottomflange of the beam lags behind it in coming

up to bath temperature. As a result, the

tube material is expanding fast, but the

cooler bottom flange is unable to keep

pace. If such a beam were to be galva-

nized in the configuration shown, it would

experience upward bowing distortion.

Prevention:

This problem can be prevented in any of

three ways, depending upon economics

and desire to maintain the integrity of the

corrosion protection:

(a) Galvanize the sections back-to-back if

there are a number of identical pieces on

the order that allow this to be an option.

Beams would be bolted back-to-bac

using pie spacers to separate the bea

to allow the flanges to be cleaned an

galvanized. The bolts would be remo

after galvanizing when the sections h

cooled. Spots where the spacers con

the beam flanges would be repaired w

galvanizing repair material. Valmont w

be pleased to assist in the determina

of the number and size of bolts to use

Separation and touch up of the sectio

would be the customers responsibilit

unless other arrangements are made

(b) Fabricate and galvanize the I-beam

tube as separate loose pieces. Then,

them together after galvanizing. Touc

welds with galvanizing repair material

(c) Redesign the section to makeit symmetrical.

Distortion in structural channels is typ

a uniform bow in the weak direction w

the toes of the channel pointing away

the radial center. This distortion can

be minimized by the back-to-back m


9/13

Cause: Poorly Selected Pick-up Points

When a long, slender product is picked

up at both ends for transport through the

galvanizing process, a potential is created

for the product to become bowed.

When the hot, galvanized product is being

withdrawn from the zinc bath, some of the

deflection caused by the products own

empty weight can be permanently set into

the product. The yield strength of mildsteel can be temporarily reduced during

immersion in the zinc bath. The problem

is compounded in slender products that

have inadequate drainage openings that

allow a substantial weight of molten zinc to

be retained and delayed from leaving the

product during withdrawal.

Prevention:

Long, slender products should be

equipped with lifting lugs located at the

quarter points of the length of the product

to overcome the possibility of experiencing

this kind of distortion.

Drainage opening should be placed and

sized according to recommendations in

the articles of Fabricators Guide to Pipe

and Tube Galvanizing and Fabricators

Guide to Open Section Galvanizing to

minimize containment

of excess zinc.

Cause: Poor Laydown

After Galvanizing

Permanent deforma-

tion may occur when a

batch of hot galvanized

products is laid down haphazardly and

flexed out of shape during cooling.

A structural member set down on its side

on blocks that are too far apart can easily

sag in its weak direction under its own

weight. If it is set down that way while still

hot, it may permanently retain some por-

tion of that distortion.

Prevention:

In both cases, this type of problem c

be reduced by arranging the parts aft

galvanizing as straight and as free fro

external forces as possible during co

When a product has acquired an une

pected bow during galvanizing, settin

it down while hot and applying weigh

to restore the part to straightness du

cooling may be helpful.


Upon request, Valmont will provide he

to customers about countermeasure

distortion during the fabrication of an

Section A-A

Cause: Thick and Thin Material

in Assembly

Thin material in an assembly expands faster

than thicker materials nearby because it

takes less time to be fully heated to the

galvanizing temperature. Distortion will take

place in thin material when thicker material

restrains it from free expansion.

Consider the case of a steel sheet or plate

placed on a structural frame and securely

attached by welds around it s perimeter.

Imagine that the sheet or plate is only

half as thick as the material in the frame.

The sheet soon reaches the galvanizing

temperature of about 850 F and its

maximum potential expansion. The frame,

being thicker, is still cooler and has not yet

had the opportunity to expand as muchas the sheet. Since the sheet cannot push

its growth outwards at the edges because

of the welds, its increase in size results in

one or more buckles in the sheet surface.

Distortion due torestrained expansion.

Section A-A

Prevention:

Two approaches can be taken to avoid

this condition.

(a) Galvanize the sheet and frame separately

and join them after galvanizing.

(b) Use the same thickness of material

for frame and sheet.

Cause: Size of Assembly Requires

Double Dip

The potential for warpage increases when

an item is so large that the galvanizer must

dip one portion at a time in order to fully

coat it.

The portion immersed in the zinc is sub-

jected to much higher temperature and

greater thermal expansion than the portion

projecting from the kettle, especially during

the first dip. The differential heating and

expansion between the two portions can

cause distortion that will not be removed

when the remainder of the product is

placed into the molten zinc.

Simple pipes and poles do not experience

distortion from double dipping, probably

because of their symmetry and simplicity

of design.

Whenever possible, it is preferable to size a

product so that it can be totally immersed

in a single dip.

Even though a product is small enough to

be immersed in a single dip, it is important

that fill and drain holes be large enough to

enable the part to be immersed and with-

drawn rapidly to avoid differential expansion.

L

1/4 L1/4 L

Considering the volume of products that arehot dip galvanized, the occurrence of distortion isquite infrequent. When it does happen, however,distortion is a serious concern to the fabricator andgalvanizer alike, involving extra costs and possiblydelays to remedy the problem.


10/13

Part 1 General

1.01 Scope

These guidelines cover the galvanized

coating applied to general steel articles,

structural sections, fabricated steel

assemblies and threaded fasteners.

Note: These guidelines do not apply to the

galvanized coating on semi-finished prod-

ucts such as wire, tube or sheet galvanized

in specialized or automatic plants.

1.02 Quality Assurance

A.Relevant Standards:

American Society for Testing and

Materials (ASTM)

A 53 Pipe, Steel, Black and

Hot-Dipped Zinc Coated

Welded and Seamless

A 123 Zinc (Hot-Dip Galvanized)

Coatings on Iron and

Steel Products

A 143 Safeguarding Against

Embrittlement of Hot-Dip

Galvanized Structural Steel

Products and Procedure for

Detecting Embrittlement

A 153 Zinc Coating (Hot-Dip) on Iron

and Steel Hardware

A 325 High Strength Bolts for Structural

Steel Joints

A 384 Safeguarding Against Warpage

and Distortion During Hot-Dip

Galvanizing of Steel Assemblies

A 385 Providing Quality Zinc

Coatings (Hot-Dip)

A 563 Carbon and Alloy Steel Nuts

A 780 Repair of Damaged Hot-Dip

Galvanized Coatings

B 6 Zinc (Slab Zinc)

B. Certification

When requested by the purchaser/

designer, a Certificate of Compliance shall

be provided stating that the galvanizing

complies with ASTM Specifications and

Standards and all other applicable

requirements specified herein.

C. Inspection and Tests

Inspections, tests and samples shall

conform with ASTM A 123 or A 153 as

applicable. Inspections and tests shall

include the following:

1. visual examination of samples or

finished products, as appropriate;

2. tests to determine thickness or

weight of zinc coating per square

foot of metal surface;

3. adhesion.

1.03 Submittals

The original and two copies of Certificates

of Compliance shall be forwarded to the

Architect/Engineer.

1.04 Handling, Transport and Storage

Galvanized articles shall be loaded and

stored as follows to prevent the formation

of wet storage stain:

(a) The material shall be loaded in such

a manner that continuous drainage

could occur.

(b) In storage, the articles shall be raised

from the ground and, i f necessary,

separated with strip spacers to provide

free access of air to most parts of the

surface. They shall also be inclined in

a manner which will give continuous

drainage. Under no circumstances shall

galvanized steel be allowed to rest on

cinders or clinkers; nor shall it be stored

on wet soil or decaying vegetation.

Suggested Guidelines for Hot Dip Galvanizing

Part 2 Products

2.01 Steel Materials

A. Structural shapes, plates and bars

that are to be galvanized shall be

manufactured from steel conforming

to ASTM A 36 or A 572 except that

silicon (Si) content shall be in the range

of 0 to 0.04% or 0.15 to 0.20%, and

phosphorus (P) content in the range

of 0 to 0.02%. Steel with chemistry

conforming to the formula Si + 2.5P

0.09 is also acceptable. Mill certificates

shall be furnished.

Note: Hot dip galvanized coatings result

from metallurgical reactions between

molten zinc and steel. Galvanized coatings

formed on steel of normal reactivity havea two-part composite structure. One part,

a layer of iron-zinc alloy formed during

galvanizing, metallurgically bonds the

coating to the underlying steel. The other

part of the coating is an outer layer of

uniform appearance that has a chemical

composition similar to the zinc in the

galvanizing bath. Certain percentages of

silicon and phosphorus in the chemistry

of some steels increase the reactivity

between the steel and molten zinc during

galvanizing and produce coatings of a

different structure and appearance.

Galvanized coatings on steels with

increased reactivity, due to the silicon

and/or phosphorus levels, may be matte

grey, mixed shades of grey, or include

localized outbursts of grey colored iron-

zinc alloy in otherwise bright surfaces.

In some instances, steels with increased

reactivity produce galvanized coatings

that are very thick and consequently

brittle. Galvanized coatings on the steel

chemistries suggested in these guidelines

should have acceptable adhesion and

be substantially free from iron-zinc alloy

outbursts. However, the coatings will tend

to be thicker on steels having higher levels

of silicon. For steels with silicon content in

the range of 0.15 to 0.20%, phosphorus

may increase the steel reactivity, but

the galvanized coating should not show

substantial iron-zinc alloy outbursting.

B. Steel for fasteners shall conform to

the following ASTM specifications for

each category:

General

Category Bolt Nut

Material Material

Carbon A 307 A 563 Gr. A

Steel Gr. A or B

High A 325 A 563 Gr. DH

Streng th Type 1 or 2 or, A 194 Gr. 2H

Tower Bolts A 394 A 563 Gr. A

C. Steel for sheet metal articles shall

conform to ASTM A 569 or A 570.

D. Steel for pipe or tubing shall conform

to ASTM A 53 or A 595 Gr. A or B.

Note: Avoid use of steels with an ultimate

tensile strength greater than 150 ksi.

2.02 Zinc for Galvanizing

Zinc for galvanizing shall conform to

ASTM B 6.

2.03 Fabrication

Fabrication practice for products to be

galvanized shall be in accordance with

the applicable clauses of ASTM A 143,

A 384 and A 385. Care shall be taken to

avoid fabrication techniques that could

cause distortion or embrittlement of the

steel during galvanizing. Before fabrication

proceeds, the Architect/Engineer shall be

notified of potential warpage problems

which may require modification in design.

All welding slag and burrs shall be removed

prior to delivery to the galvanizer.

Holes and/or lifting lugs to facilitate handling

during the galvanizing process shall be

provided at positions as agreed between

the designer, fabricator and galvanizer.

Unsuitable marking paints shall be av

and consultation by the fabricator wit

galvanizer about the removal of greas

paint and other deleterious material s

be undertaken prior to fabrication.

Surface contaminants and coatings w

would not be removable by the norma

chemical cleaning process in the galva

operation shall be removed by the fab

using blast cleaning or some other me

2.04 Surface Preparation

Steel shall be prepared utilizing a cau

bath, acid pickle and flux. Where appro

the steel can be blast cleaned and flu

2.05 Galvanizing

A. Steel members, fabrications, and

assemblies shall be galvanized aft

fabrication by the hot dip process

accordance with ASTM A 123.

B. Bolts, nuts and washers, and iron

steel hardware components shall

galvanized in accordance with AS

153. Nuts and bolts shall be supp

accordance with ASTM A 194, A

A 325, A 394 or A 563, as applica

Products shall be safeguarded ag

steel embrittlement in conformanc

with ASTM A 143.

All articles to be galvanized shall b

handled in such a manner as to a

any mechanical damage and to m

mize distortion.

When the galvanizer detects desig

features which may lead to difficul

during galvanizing, he shall point

them out to the fabricator and

arrange for modifications to be

made prior to dipping.

The composition of metal in the

galvanizing bath shall not be less

than 98% zinc.


11/13

End cross section,when required

Individual areas, or allsurfaces for speciallength, at end of section

Any localized area

Entire top of flange, orany localized area

2.06 Coating Requirements

A. Thickness/Weight:The thickness

or weight of the galvanized coating

shall conform with paragraph 5.1 of

ASTM A 123 or Table 1 of ASTM A

153, as appropriate.

B. Surface Finsh:The galvanized

coating shall be continuous, adherent,

as smooth and evenly distributed as

possible and free from any defect that

is detrimental to the stated end use of

the coated article.

The integrity of the coating shall be

determined by visual inspection,

coating thickness measurements,

and adhesion testing.

Where slip factors are required to

enable friction grip bolting, these

shall be obtained after galvanizing by

suitable treatment of the faying surfaces

in accordance with the latest edition

of the Specification for Structural

Joints Using ASTM A 325 or A 490

Bolts as approved by the Research

Council on Structural Connections

of the Engineering Foundation.

C.Adhesion:The galvanized coating

shall be sufficiently adherent to

withstand normal handling during

transport and erection.

Part 3 Execut ion

3.01 Welding

Where galvanized steel is to be welded,

adequate ventilation shall be provided.

If adequate ventilation is not available,

supplementary air circulation shall be

provided. In confined spaces, a

respirator shall be used.

Welding shall be performed in ac-

cordance with the American Welding

Society publication D19.0-72, Welding

Zinc Coated Steel.

All uncoated weld areas shall be

touched up.

A. Galvstop Service

Successful welding of galvanized steel

requires pre-planned, plain, uncoated

areas conforming to fabrication

requirements. Valmonts Galvstop

service is an adaptable method to

provide specific uncoated areas of

any size, shape or location. Extra

preparation work is not required.

Requirements must be provided.

Note: Galvstop is only applicable on

external surfaces and accessible

internal surfaces.

3.02 Touch Up and Repair

A. Mechanical Damage

Areas damaged by welding, flame

cutting, or during handling, transport

or erection shall be repaired by one of

the following methods whenever the

damage exceeds 3/16 in width on flat

surfaces, or 1/10 on cut ends:

(1) Cold Galvanizing Compound

Surfaces to be reconditioned

with zinc-rich paint shall be clean,

dry, and free of oil grease and

corrosion products.

Areas to be repaired shall be

power disc sanded to bright

metal. To ensure that a smoothreconditioned coating can be

effected, surface preparation

shall extend into the undamaged

galvanized coating.

Touch-up paint shall be an organic,

cold galvanizing compound hav-

ing a minimum of 65% zinc dust

in the dry film.

The paint shall be spray-or brush-

applied in multiple coats until a

dry film thickness of 4 mils mini-

mum has been achieved. A finish

coat of aluminum paint shall be

applied to provide a color blend

with the surrounding galvanizing.

Coating thickness shall be verified

by measurements with a magnetic

or electromagnetic gauge.

(2) Zinc Based Solder


with zinc based solder shall be

clean, dry, and free of oil, grease

and corrosion products.

Areas to be repaired shall be wire

brushed and given a thin layer of

acidic paste flux.

Heat shall be applied slowly and

broadly close to, but not directly

onto, the area to be repaired.

The zinc-based solder rod shall

be rubbed onto the heated metal

until the rod begins to melt. A

flexible blade or wire brush shall

be used to spread the melt over

the area to be covered. The zinc

based solder shall be applied toa minimum thickness equivalent

to that of the undamaged coating.

Coating thickness shall be verified

by measurements with a mag-

netic or electromagnetic gauge.

(3) Metallizing


with zinc metal spray shall be

clean, dry, and free of oil, grease

and corrosion products.

The area to be repaired shall

be grit blasted to white metal,

followed by zinc metal spraying

to a coating thickness equivalent

to that of the undamaged coating,

and seal coated using an alumi-

num vinyl paint.

B. Wet Storage Stain

Any wet storage stain shall be

removed by the galvanizer if formed

and discovered prior to leaving the

galvanizers plant, unless l ate pick-up

or acceptance of delivery has neces-

sitated the material being stored in

unfavorable conditions. In any event,

wet storage stain shall be removed

before installation to prevent premature

failure of the coating. Wet storage stain

shall be removed as fol lows:

(1) The objects shall be arranged

so that their surfaces dry rapidly.

(2) Remove light deposits with a stiff

bristle (not wire) brush. Heavier

deposits are to be removed by

brushing with an acidic-basedmetal cleaner. The surfaces

cleaned shall be thoroughly

rinsed with water.

(3) A coating thickness check must

be made in the affected areas to

ensure that the zinc coating

remaining after the removal of

wet storage stain is sufficient to

meet or exceed the requirements

of the specification.


12/13

Notes


13/13

7002 North 288th Stree

Valley, NE 68064 USA

p 1.800.825.6668

f 1.402.359.6070

www.valmontcoatings.com

Documents

Valm Coat Galvtech 102804