Among all the alloying elements which have an effective effect on corrosion resistance, Cu is one of the most effective elements. In the industrial atmosphere and even in the marine atmosphere, the corrosion resistance of corten A588 steel with 0.2%-0.4% Cu is better than that of ordinary carbon steel without Cu.
At present, there are two main mechanisms of the effect of copper on the corrosion resistance of corten A588 steel: one is the theory of promoting anodic passivation, Tomashow believes that the secondary precipitation of copper on the surface of steel forms a cathode, which can promote the anodic passivation of steel contacted with it, thus forming a rust layer on the surface of steel to improve its corrosion resistance; the other is the theory of enrichment of copper elements. Yin Zun et al. simulated the marine atmospheric environment by accelerated corrosion test in laboratory, and explored the marine atmospheric corrosion properties of two kinds of high strength and low alloy steels containing copper.
It is found that the steel containing the most copper exhibits the best corrosion resistance, which is considered that the element of copper is enriched in the internal rust layer in the form of CuO in the steel. It can isolate the corrosive medium and reduce the promotion of Cl-corrosion, and increase the polarization resistance of the steel, which leads to the enhancement of the protection of the rust layer, thus improving the marine atmosphere corrosion resistance of the corten A588 steel.
Liu Guochao et al. found that when dry-wet alternating test was carried out in simulated marine environment, the corrosive medium with water content on corten A588 steel surface would alternately change with temperature and humidity, while the electrochemical reaction of rust on corten A588 steel surface would occur continuously. The alloying of copper can accelerate the reduction of some components of the rust to Fe3O4 in the cathode, thus promoting the formation of continuous internal rust layer containing more Fe3O4, and inhibiting the oxidation of anodic iron to rust by improving the adhesion of surface rust layer, so as to improve the corrosion resistance of corten A588 steel in marine environment.
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