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Development of a new electrodeposition process for plating of Zn-Ni-X (X = Cd, P) alloys : Permeation characteristics of Zn-Ni-Cd ternary alloys

It is shown that an electrodeposited Zn-Ni-Cd alloy coating produced from sulfate electrolyte inhibits the discharge of hydrogen on carbon steel. The newly developed ternary alloys have approximately ten times higher corrosion resistance when compared to a Zn-Ni alloy. Hydrogen permeation characteri...

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Bibliographic Details
Published in:Journal of the Electrochemical Society 2000-12, Vol.147 (12), p.4507-4511
Main Authors: DURAIRAJAN, A, HARAN, B. S, WHITE, R. E, POPOV, B. N
Format: Article
Language:English
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Summary:It is shown that an electrodeposited Zn-Ni-Cd alloy coating produced from sulfate electrolyte inhibits the discharge of hydrogen on carbon steel. The newly developed ternary alloys have approximately ten times higher corrosion resistance when compared to a Zn-Ni alloy. Hydrogen permeation characteristics of Zn-Ni-Cd alloy coatings were studied and compared with those of a bare and a Zn-Ni alloy coated steel. The transfer coefficient, alpha , exchange current density, i sub 0 , thickness dependent adsorption-absorption rate constant, k'', recombination rate constant, k sub 3 , surface hydrogen coverage, theta sub H , were obtained by applying a mathematical model to experimental results. Alloys obtained from baths containing higher concentration than 3 g/L of CdSO sub 4 in the sulfate plating bath are seen to have superior permeation inhibition properties compared to the Zn-Ni alloy coating and bare steel. The hydrogen permeation current was zero under normal corroding conditions for Zn-Ni-Cd alloy and it increased to 0.3 mu A/cm exp 2 at a cathodic over-potential of 250 mV. The hydrogen permeation current density for steel and Zn-Ni alloy under similar conditions were 62.1 and 1.3 mu A/cm exp 2 , respectively.
ISSN:0013-4651
1945-7111
DOI:10.1149/1.1394093