The Effect of Electroplating of Cr and Sn on Corrosion Resistance of Low Carbone Steel (CK15)- Hani Aziz Ameen

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AMERICAN JOURNAL OF SCIENTIFIC AND INDUSTRIAL RESEARCH© 2010, Science Huβ, http://www.scihub.org/AJSIR

ISSN: 2153-649X doi:10.5251/ajsir.2010.1.3.565.572

The effect of electroplating of Cr and Sn on corrosion resistance of low

carbon steel (CK15)

Hani Aziz Ameen1, Khairia Salman Hassan2 and Bushra Rasheed Mohameed3

1 Technical College – Baghdad - Iraq .E-mail:[email protected]

2 Institute of Technology – Baghdad / Mechanical Dept.-Iraq.E-mail:[email protected]

3 Institute of Technology – Baghdad / Mechanical Dept.-Iraq.E-mail:[email protected]

ABSTRACT

The aim of the research is to study of electroplating of Cr and Sn on the electrochemicalcorrosion resistance of low carbon steel (DIN CK15) specimens of (0.2x1.5x1.5) cm dimensionswere fabricated to test the electrochemical corrosion. A number of such specimens were coatedwith tin (Sn) and chrome (Cr) separately to find out the electrochemical corrosion of the metal and

the influence of the elements of metal coating on this rate, then passing an electric current in anelectric cell representing the positive electrode. The negative electrode was of platinum at apotential, then limiting it through passing a current in the open circuit. The potential is comparedwith the potential of the metal is the electrochemical chain. Then the circuit is closed and anelectric current at this potential is passed with an increasing +100 volt , –100 volt, and finding thecorrosion current through the intersection contacts to the cathodic and anodic electrode inaccordance with Tafel's method and calculation of corrosion rate. The plating acts as an anodeelectrode to protect the steel from corrosion. It was deduced that the coating elements leads todecrease of corrosion rates in comparison to the non-plated metal. The chrome led to greaterdecrease from tin element in the corrosion rate, the existence of alloying in the metal contributedat increasing the corrosion rate.

Keywords: Corrosion, electroplating, low carbon steel

INTRODUCTION

Steel is widely used in engineering applications at85%. It needs methods to protect it from corrosion forthe limited resistance (Ndaliman, 2006). Steel is usedin fabrication of components of marine and landtransportations in oil pipelines and structures ofbuilding, bridges, etc. Due to the steel's importance inengineering applications and its non- resistance tocorrosion in most media, researches were concernedin the study of its resistance to corrosion andcalculation of cost of protection. Corrosion is a failurethat inflects the metal due to a chemical reaction of

electrochemical reaction with its medium. Chemicalcorrosion is due to a reaction between the metal oralloy with the environment. Electrochemical corrosionis due to an electric current to which the a metal isexposed to due to application of an external potentialor corrosion due to galvanic reaction or focus cells.Corrosions adopts several forms depending on thenature of the corrosion and condition forms situations

of the media. The corrosion types are (AlstomBosch,2000): (1) Atmospheric Corrosion (2) UniformCorrosion (3) Galvanic Corrosion (4) CreviceCorrosion (5) Intergranular corrosion (6) Exfoliationcorrosion (7) Erosion–Corrosion (8) Stress CorrosionCracking (9) Corrosion Fatigue (10) FiliformCorrosion (11) Microbiological Induced Corrosion.Fig.(1) shows the photos of these kinds of corrosion.

There are factors that influence corrosion rate in theliquid media, e.g. acidic (pH) as well as rate of mediaof the submerged media in it and temperature of themedia and existence of alloy metals in the metal. The

pH is an important factor in case the media's pH islow because the amount of hydrogen increase theaverage corrosion rate, i.e. the form is sustainedwhile for the alkai media, the corrosion would beslower. Corrosion of steel in sea water differs fromthat in pure water, because sea water is a goodelectric conductor, the pit form will be larger and theconcentration of the cell works for long distances.



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This conductivity leads to non-uniform attack incomparison with pure water, the cyclic turning during

submerging due to air motion causes many pits incomparison by continual submerging.

Exfoliation Corrosion Crack Initiation From The Pit Root Corrosion Fatigue

Burleigh et al (1995) At Weld Pool (Abhay,2007) (Rollason,1973)

Filiform Corrosion Microbiological Induced Corrosion Pitting Corrosion

Roland et al ,2000) (Alstom Bosch,2000) (Michel Jacques,2004)

Crevice Corrosion Interganular Corrosion Galvanic Reaction

(Rollason,1973) Burleigh et al (1995) (Abhay,2007)

Fig.(1) Types of Corrosion

Prabhu Ganesan et al, 2007, are studied the effect ofmultilayer Zn-Ni coatings in 5% NaCl solution usingelectrochemical corrosion techniques. In the currentresearch; electroplating is the sedimentation of alayer of the metal to be plated with by an electrolysis

process for a solution containing the dissolved metalsalt; thus the alloy's base surface gains thespecification and characteristics of the metal bywhich it is plotted. Electroplating is a commonmethod which was developed to be sophisticated



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non- reliant on a chemical reaction between theplating metal and the base alloy.Therefore, the metal surface should be prepared forthe electroplating process.Plating process is summarized by electric

sedimentation by making the metal which is requiredfor plating a cathode submerged in a liquid consistingof solution of the salts of the plating metal. This is anelectrolyte with addition of some catalysts. Thesemay additive that improve the characteristics of theplating surface or exciting materials for reaction. Themetal to be sediment is attached to the anode is theelectroplating cell.

In the current research, study is conducted of theinfluence of the plating process on corrosion rate andto investigated the effect of the plating element, e.g. ,chrome and tin on the corrosion rate.

Experimental PartThe experimental part is summarized as follows:Metal SelectionA low carbon steel (DIN CK15) was chosen. Byknowledge of the chemical composition of the metal,the metal is analyzed by an optical spectrograph. Thechemical composition of the metal is shown intable(1).

Table(1) Chemical composition of carbon steel (DIN CK15)

Preparation of Test SpecimenMany test specimen of steel used according to thestandard specification for testing (ASTM) wereprepared. The test specimen dimension are1.5x1.5x0.2 cm.

Categorization of SpecimenAfter complete preparation of the specimen (cuttingthe plate and preparing them for plating process),

they are categorized into three groups as shown intable (2) .

Table (2) Categorization of specimen according togroups

State of Specimen Specimen's symbol

Specimen of low carbon steelwithout plating

A

Specimen of low carbon steelwith tin plating

B

Specimen of low carbon steelwith chrome plating

C

Tests and Checks: Preparations of specimens for

microscopic test inclusive:1- Grinding the specimen by polishing paper

180-250-400-800-1000 with use of water.2- Polishing operation by use a special

polishing cloth with use of alumina solution(aluminum oxide Al2O3. The granules size is0.3 µ.

3- Developing operation : use of Netal solution(2% nitric acid + 98% ethyl alcohol)

Plating Process: Electroplating (Lowen, 1978)was performed on the specimens groups ofsymbol (B,C) of table(2) . This process consistsof the following stages:A- Cleaning the specimen by an alkali solution,

consisting of sodium carbonates (Na2CO3) by

a weight ranging between 30-45 gm/L and trisodium phosphate (Na3PO4H2O) by a weightranging between 30-45 gm/L and sodiumhydroxide (NaOH) by a weight rangingbetween 7.5-15 gm/L inside anelectrochemical cell. The specimenrepresents the cathode electrode, the anodeelectrode made of stainless steel by use of6V to eliminate oils and organic impuritiesfrom the specimen's surface.

B- Washing by cold water through submergingby water to stop the reaction of the alkalisolution.

C- Submerging the specimens in a dilutedsolution of hydrochloric acid 15% for 15minutes to remove the remaining alkalisolution and preparation of the surface forthe plating process.

D- Water washing for the same purpose in thenext stage.

E- Preparation of the cell : The plating cellconsists of a 20x20x20 cm cubic tank

Element % ,

wt %C Mn P S Ni Cr Si Mo Cu V

low carbonsteel

0.169 0.683 - 0.014 0.004 0.024 0.193 0.054 0.022 0.002



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containing two poles made of lead. Thespecimen for plating is attached to thenegative electrode. The positive electrode isattached to the DC power supply. Platingsolution are added inside a container with

less than 0.5 liter water to dissolve thesolution in water. Thereafter, the half liter iscompleted and heated to a temperature andperiod according the plating solution for eachspecimen.

F- Plating Process : The plating process wasperformed by tin and chrome elements eachindividually in accordance with the platingconditions as shown in table(3)

Corrosion TestA- Preparation of corrosion solution

The corrosion solution in which submerging

shall be conduction is prepared of sea water(3.5% NaCl) consisting of 35 gm of sodium

chloride salt with 100gm distilled water withpH of 6.9 by measure by a pH meter.

B- Electrochemical corrosionElectrochemical corrosion by Tafel method:

An electric current is passed in anelectrochemical cell (Fig.(2)) consisting of:1- A positive electrode representing the

specimen to be tested (working electrode) (anode)

2- A negative electrode representing thepole in which the electrons which werereleased from the anode electrode aregathered. A platinum poles was used inthis cell ( auxiliary electrode) (cathode) .

3- Standard calomel electrode .4- An electrolyte of sea water5- Electric power supply.

Table(3) Plating conditions

Element Time (min.) Current density (Amp/cm2) Temperature

(°C)Voltage

(volt)

Tin (Sn) 7 25 70 6

Chrome (Cr) 7 7 25 6

Fig.(2) Electrochemical cell

C. Preparation of specimen for corrosion test: Anelectric current with a potential to be determined(according to the metal type ; low carbon steel DINCK15) is passed. Upon passage of current, thepotential differences shall change indicating that thiscurrent has led to corrosion which was measured. Itrepresents the corrosion current (Icorr). It depends on

Tafel method (by use of potentiostat) in themeasurement of corrosion rate through takingcontacts for anodic and cathodic curves. Theintersection point represents the corrosion current.RESULTSFig.(3)shows the microstructure by a light microscope

of 400X magnification. Fig.(4) shows the photos of the





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Fig.(5) Results of electrochemical corrosion for low carbon steel specimens



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Fig.(6) Comparison of Tafel curves for the different specimens of low carbon steel

DISCUSSIONFrom the results of the post- electrochemicalcorrosion conduction the low- carbon steel shown intable(4), corrosion photos in Fig.(4) and Fig.(5), it wasfound that the corrosion rate for specimens of group Ais greater from that of specimens of group B which are

tin- plated and that of specimens of group C which arechrome-plated. This is due to existence of alloyingelements in the metal of low resistance to corrosion.One method adopted to delimit of metal corrosion isthe use of plating. Tin and chrome used as platingelements behave as electrodes (anode), and steel asnegative electrode because both are above steel isthe electrochemical series. Sea water is an acidic

medium of good electric conductivity, that iselectrolyzed to ions of the positive metal whichcombine with the negative ions of oxygen in theelectrolyte forming metal oxides which representcorrosion. Plating process contributed at decreasingthe corrosion rate, the correct choice of the plated

element is to be according to the location of theelement in the electrochemical process by renderingit, the element on which corrosion occurs.

1E-3 1E-2 1E-1 1E+0 1E+1

current density / A / cm

-775

-725

-675

-625

-575

-525

-475

-425

-375

-325

-800

-750

-700

-650

-600

-550

-500

-450

-400

-350

-300

p o t e n t i a l s / m v v s

S C E

carbon steel (H)carbon steel (H)-Cr coatedcarbon steel (H)-Sn coated

µ 2



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CONCLUSIONS1- It gave to plating elements a decrease in

corrosion rate compared to the metal withoutplating.

2- Chrome elements gave a decrease greater

that of tin element in corrosion rate.3- Existence of alloying elements on the metal

contributed to an increase in corrosion rate.

REFERENCES[1] Ndaliman M. B. ”An assessment of Mechanical

Properties of Medium Carbon Steel under DifferentQuenching Media”, AUJ. T. , 10(2), 100, Oct 2006.

[2] Alstom Bosch "Corrosion of Carbon Steel” , Key toMetals Steel,2000.

[3] Michel Jacques “Corrosion of Aluminum", Paris,France, 2004.

[4] Rollason E.C. "Metallurgy for Engineering”, EdwardArnold Publishers, 4th Edition, 1973.

[5] Burleigh T. D., Ludwiczak E. and Petri R.A."Intergranular Corrosion of an Aluminum-Magnesium-Silicon Copper Alloy”, Corrosion Science,Vol.51, No.1, January 1995.

[6] Abhay K. Tha , Naga G. and Shiresha K. “StressCorrosion Cracking in Aluminum Alloy, AFNOR 7020-T6 water tank adaptor for liquid propulsion system”organization trivandrum ,G95.022 India, May 2007.

[7] Roland J. and Huggins, P.E. “Microbiology Influencedcorrosion”, What its and how works, 2000.

[8] Prabhu Ganesan , Swaminatha P. Kumaraguru, BrankoN. Popov " Development of Compositionally ModulatedMultilayer Zn-Ni Deposits as Replacement forCadmium", Surface and Coatings Technology, 201, pp7896-7904,2007.

[9] Lowen Heim F.A "Electroplating ", Mc Graw-Hill , NewYork , 1978.

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The Effect of Electroplating of Cr and Sn on Corrosion Resistance of Low Carbone Steel (CK15)- Hani Aziz Ameen