Papers by Author: Jia Wang

Abstract: Under immersed and we-dry cyclic conditions, the deterioration processes of the organic coating on carbon steel surface have been comparatively studied using electrochemical techniques. The wet-dry cycles were carried out by exposure to 4 h immersion and 4h dryness (4-4h cycles) and 12h immersion and 12h dryness (12-12h cycles) conditions, respectively. The immersion condition was carry out in a 3.5% NaCl solution and drying at 298K and 50% RH. According to the EIS characteristics, the entire deterioration processes under above three mentioned conditions can be divided into three main stages, consisting of the medium penetration, corrosion initiation and corrosion extension. Comparing with the immersed, the 4-4h wet-dry cycles greatly accelerated the entire deterioration process; especially during the corrosion initiation and the corrosion extension periods, leading the paint system lose its anti-corrosive performance in a short period. However, the 12-12h wet-dry cycles decelerated the entire deterioration process, prolonging the coatings anticorrosive ability. The acceleration mechanism of the coatings and underlying metal corrosion under wet-dry cycles was discussed based on the above results.

Abstract: In natural seawater environment, temperature and chlorine ion are important factors for organic coating degradation. The alternating pressure of seawater can also affect the lifetime in deep-sea environment and probably is conducive to synergistic effects with other ageing factors. The present work is to investigate the effect of alternating pressure of seawater on protective properties of epoxy organic coating on 907A steel substrate, and evaluates the organic coating degradation process after pressure tests at atmospheric pressure. EIS was used to study the degradation process of the organic coating in natural seawater. The results demonstrated that the impedance of coating under alternating pressure of seawater conditions decreased faster than that at atmospheric pressure. With the increase of alternating pressure cycles, the entire degradation process of organic coating was accelerated. It is concluded that alternating pressure of seawater has to be considered as an aggressive factor like temperature or chlorine ion.