Why is the corrosion resistance of 05CuPCrNi weathering steel very strong?

The main purpose of adding Cu and P to 05CuPCrNi weathering steel is to improve corrosion resistance and strengthen ferrite by solution.

1. Cu is the main and widely used alloy element to improve the atmospheric corrosion resistance. The addition of Cu in 05CuPCrNi weathering steel can form a dense copper oxide thin layer between the corrosion layer of steel and the copper accumulation layer, so as to slow down and inhibit the corrosion of medium to the 05CuPCrNi weathering steel.

2. When the content of Cu is more than 0.15%, the atmospheric corrosion resistance is improved slowly. P is an effective element to improve the atmospheric corrosion resistance of alloy elements, and is an anode depolarizer. In electrolyte solution, it can accelerate the uniform dissolution of steel and the oxidation rate of iron, and help to form a uniform corrosion layer on the surface of steel, and has a clear boundary with the inner rust layer, so as to improve the corrosion performance of steel.

3. If Cu content in 05CuPCrNi weathering steel is controlled within 0.25% - 0.35% and P is controlled within 0.07% - 0.10% according to the lower limit, it can meet the requirements of atmospheric corrosion resistance. Cr is also one of the alloying elements to improve the atmospheric corrosion resistance of low alloy steel, but it has obvious effect only when Cu element is combined. The corrosion potential of Cr is low, and it is a passivation element, which promotes the formation of dense oxidation passivation film on the surface of steel in the atmosphere, so as to improve the corrosion resistance of steel.

4. In the process of atmospheric corrosion, the content of Cr is controlled at 0.30% - 0.45%, and Ni is also one of the effective alloy elements for atmospheric corrosion resistance. When the Ni content is S1% and the steel contains Cu, the effect of improving the corrosion resistance is not obvious. However, the alloy phase can be formed when the ratio of Ni to Cu is 1:3, so the cracking of steel containing 0.3% Cu can be prevented by controlling the content of Ni more than 0.1%.