Theoretical Investigation of Under-film Corrosion on Zn, Zn-Fe Alloy Coated Steel Sheets

Abstract

For the purpose of the theoretical explanation on Cl^- penetration behavior of Zn and Zn-Fe alloy coating investigated phenomenologically, the modeling of coating corrosion at under-film corrosion tip has been attempted and the balance of corrosion current by way of two micro circuits was formulated.
The coating corrosion distance (Cl^- penetration distance) and the effective length of the iron substrate contributing the formation of corrosion circuit between coating and iron substrate, the distribution ratio of corrosion current by way of circuit on coating to total coating corrosion current were required quantitatively.
As a result, it made clear that the physical shap of coating corrosion circuit was defferent between atmospheric exposure and salt spray environments.