Performance of Sulfide Stress Corrosion Resistance of Zn-Al Two-Layer Coating and Al Coating

Stress corrosion tests were made to compare the performance of Zn-Al two-layer costing with that of Al coating in H₂S-containing NACE solution. The results of tests show that Zn-Al two-layer coating(not as we expected) neither remains the advantages of Zn and Al coatings nor offsets the disadvantages of them. In fact when corrosive permeates the Zn layer of Zn-Al tWo-layer coating, preferential solution of Zn layer will take place, which results in the crevice of Al layer, further, the failure of the whole coating. This paper discussed the stress corrosion failure of Zn-Al two-layer coating in H₂S-Saturated aqueous solution, and pointed out the irrationality of the design of Zn-Al two-layer coating..