Compositional and Microstructural effect on atmospheric corrosion of weathering steel

The chemical composition and microstructure of weath-ering steel effecting on atmospheric corrosion resistance were investigated. The elements in weathering steel stron-gly influenced on environmental resistance as follows : Cr (0.45-0.75%),Ni (0.42-0.78%), Cu (0.44-0.62%), P (0.17-0.23%) and RE (1.3-2 kg/t). The stabilization of WS firrite matrix with regular small grain size had improved atmospheric corrosion resistance.
The addition of copper made rapid phase transformation of rust layer to firm state. The surface rust layers conta-ined adequate basic elements such as Si,Cr, Ni, Cu and P affecting surface protection, so improved corrosion resist-ance of WS in marine and industrial atmospheres.

Copper enhanced higher corrosion resistance in marine atmosphere than other elements, it created the compounds such as Cu4(SO4)(OH)6 and Ni4(SO4)(OH)6.

Chromium and Fe formed α-(Fe1-xCrx)OOH compound with nanoparticle size, therefore had stabilized rust layer covering on WS matrix.
Rare earth metals (about 2 kg/t) increased pH in elect-rochemical area and passively formed phosphide layers clingging and covering on the surface, thereby improved corrosion resistance.