Approach to the Development of Corrosion Resistance of Fe-Zn Alloy Coating from Corrosion Science

Abstract

The corrosion resistance of zinc and zinc alloy coatings in natural environment depends on the properties of corrosion product layer found on the surface. The type and amount of corrosion products, adhere to the surface, influence the barrier effect of corrosion layer. The amount of zinc hydroxide and basic zinc chloride, Q, could be determined by cyclic cathodic polarization method on the basis of the finding that adherent corrosion products were reduced in response to the electrode potential. A new function of compactness of corrosion layer, C=Q/I_corr., was introduced in order to evaluate the barrier effect of corrosion product layer.
Nickel was selected as an additional element, which developed the corrosion resistance of Fe-Zn alloy coating, from the values of I_corr. and C determined of corroding zinc specimens in the solution containing iron and other metallic ions.
1 wt% nickel addition to Fe-Zn alloy coating enhanced the corrosion resistance of coating.
And a new function of compactness, C, was useful to evaluate the barrier effect of the corrosion product layer for oxygen diffusion.