Abstract
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, α, exchange current density, , thickness dependent adsorption‐absorption rate constant, k″, recombination rate constant, , surface hydrogen coverage, , were obtained by applying a mathematical model to experimental results. Alloys obtained from baths containing higher concentration than 3 g/L of 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 at a cathodic overpotential of 250 mV. The hydrogen permeation current density for steel and Zn‐Ni alloy under similar conditions were 62.1 and , respectively. © 2000 The Electrochemical Society. All rights reserved.
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