Initial stages of localized corrosion at cut-edges of adhesively bonded Zn and Zn-Al-Mg galvanized steel

• Published in: Electrochimica acta 2016-09, Vol.211, p.126-141
• Main Authors: Yasakau, K.A., Kallip, S., Lisenkov, A., Ferreira, M.G.S., Zheludkevich, M.L.
• Format: Article
• Language: English
• Subjects: adhesive; cut-edge; galvanized steel; in situ AFM; localized corrosion
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2016.06.045

•First steps of localized corrosion were studied at (Zn and Zn-Al-Mg) galvanized steel cut edges by in situ AFM.•Zinc solid solution shows localized pitting attack at Zn and Zn-Al-Mg cut edges.•Eutectics show selective dissolution at Zn-Al-Mg cut edge.•Buried zinc/adhesive interface shows local corrosion at zinc solid solution and eutectic phases.•The decrease in corrosion kinetics was attributed to the corrosion products film on zinc and steel The mechanisms of the initial stages of localized corrosion at cut edges were investigated for adhesively bonded Zn (Z) and Zn-Al-Mg (ZM) galvanized steel. The results provided strong evidence for the localized nature of corrosion of galvanized coatings at the cut edges and at the adhesive/zinc interface. In both cases a defined localized corrosion attack on zinc in Z sample was observed. On the contrary, in the case of the ZM specimen both zinc solid solution and eutectics exhibited local corrosion. The local attack at the adhesive/Z(ZM) interface was correlated with an anodic undermining process. It develops near the cut-edge surface and at the buried deep adhesive-zinc interface and results in adhesive disbonding in the buried interface. The electrochemical studies revealed that the corrosion kinetics at the metal cut-edges decreases during immersion, which could be due to formation of corrosion products on both steel and zinc surfaces.