Copper ion accelerated local failure of epoxy coating on NdFeB magnet in immersion conditions
By Yang, Lin; Wang, Zi Ming; Shi, Linshe; Zheng, Dajiang; Fu, Donghui; Song, Guang-Ling
Published in Engineering Failure Analysis
2020
Abstract
Fast evaluation of organic coating protectiveness on metals is highly demanded for industry. In this paper, a simple immersion method is presented to accelerate the local failure of coatings in a Cu2+-containing solution. The experimental results show that in epoxy coatings on NdFeB magnet, the Cu2+ ion can significantly accelerate the local blistering process, and some of the blisters can continuously grow and finally rupture in the marginal edges or the top of the blisters. These local failure events are more likely to occur near the edges and rarely appear in the central area of a coating sample. An electrochemical-mechanical interaction model is proposed to interpret the local blistering and rupturing processes, in which the accelerated coating failure is attributed to the local galvanic corrosion induced by Cu particles deposited on the substrate and the local delamination of the coating.