Effect of Environmental Conditions on the Corrosion near Shear Cut Edge of 55 mass% Al–Zn Alloy Coated Steel Sheets

Abstract

The purpose of this study is to clarify the effect of dry and wet processes on the mechanisms of edge corrosion of hot dip 55 mass% Al-Zn alloy coated steel sheet. The corrosion tests employed were continuous salt-spray tests and cyclic corrosion tests using NaCl solution or artificial seawater. It was confirmed that the edge corrosion is suppressed during the salt-spray test using artificial seawater. Furthermore, the suppression was not prevented by dry and wet processes. In order to reveal the corrosion mechanisms, the galvanic current and the cathodic polarization curves at exposed steel were measured and the corrosion products were characterized. It is suggested that the artificial seawater forms anti-corrosive corrosion products and that suppress the cathodic reaction on the steel which is exposed on the shear cut edge. The corrosion products are not changed by dry and wet processes. The numerical analysis also revealed the influence of the dry and wet process on edge corrosion.KEY WORDS: 55 mass% Al-Zn alloy coated steel sheet; edge corrosion; artificial seawater; salt-spray test; dry and wet processes; numerical analysis; X-ray diffractometry (XRD); Fourier transform infrared spectroscopy (FTIR)

Mechanism of Corrosion Protection at Cut Edge of Zn-11%Al-3%Mg-0.2%Si Coated Steel Sheets

“…5. This agrees with the finding 10) that the corrosion of the coating adjacent to the cut edge was suppressed by the inhibition of the cathodic reaction on 55%Al-Zn-alloycoated steel sheets.…”