Failure behavior of several epoxy organic coatings in ocean pressure environments

摘要

Extensive exploration of deep ocean resources is greatly hindered by the unique and special conditions in deep ocean environments, including relatively low temperatures, diverse dissolved oxygen levels, and high hydrostatic pressure. Amongst these unique properties, the high pressure is the major factor in terms of the corrosion performance of metallic structures applied in the deep ocean environments. The practice organic coating is one of the most important methods for corrosion protection in marine environments. However, at present, the studies of organic coating under high hydrostatic pressure or alternating pressure have not received much attention. The failure of several organic coatings with different fillers on mild steel under high hydrostatic pressure (63 atm) and alternating pressure (63 atm-1atm), has been studied compared with that under atmospheric pressure (1 atm), using impedance measurements, gravimetric testing, adhesion testing and scanning electron microscopy (SEM). The results show that hydrostatic pressure promotes diffusion of water in the coating, which speeds up water spread and electrochemical reactions at the interface. Alternating pressure firstly destroys the interface between coating and metal to decrease the adhesion of coating. It following destroys the interface between organic resin and inorganic fillers to decrease the compactness of the coating. In order to promote the serving properties and prolong the serving life, a new coating with chemical-bonding interfaces has been studied for deep ocean. A theoretical calculation ways to predict the lifetime of coatings has also modeled by mathematic functions.