Salt spray corrosion and electrochemical corrosion performances of Dacromet fabricated Zn–Al coating

Abstract

Purpose This study aims to investigate the salt spray corrosion (SSC) and electrochemical corrosion of obtained Zn–Al coating, which provided a basis for comprehensive analysis of corrosion behavior of Zn–Al coating. Design/methodology/approach A Zn–Al coating was fabricated on Q235A steel using a Dacromet method. The SSC and electrochemical corrosion performances in 3.5 Wt.% NaCl solution were investigated using an SSC chamber and electrochemical workstation, respectively, and the corrosion mechanism of Zn–Al coating was discussed. Findings The Dacromet fabricated Zn–Al coating is primarily composed of Zn and Al phases, its residual stress of −11.1 ± 4 MPa is compressive stress, which is beneficial to improve its corrosion resistance. In the SSC process, the corrosion product of Zn5(OH)8Cl2H2O enhances the corrosion resistance of Zn–Al coating, which provides sufficient cathodic protection for the substrate. The corrosion potential of Zn–Al coating is lower than that of substrate, which provides sufficient cathodic protection to the substrate, the Zn–Al coating in the immersion periods is protected by the corrosion product and Zn–Al sheets. Originality/value In this study, a Zn–Al coating was first fabricated on Q235A steel using a Dacromet method.

Corrosion performance and morphological analysis of activated zinc phosphate coating formed on steel surface

“…In the Nyquist diagram, the semicircles obtained for all tested substrates are not well defined. The impedance diagram describes the kind of electrochemical reactions occurring on the coating and metal-solution interface, which are directly related to the corrosion resistance (Liu and Kong, 2019). The high frequency capacitance loop is related to the deposition of phosphate coating on the substrate surface, and the low frequency inductance loop is attributed to the formation of corrosion products on the exposed surface (Sheng et al , 2011).…”