Compositional and microstructural effect on atmospheric corrosion of weathering steel

The chemical composition and microstructure of weathering steel effecting on atmospheric corrosion resistance were investigated. The elements in weathering steel strongly 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 contained adequate basic elements such as Si, Cr, Ni, Cu and P affecting surface protection, so improved corrosion resistance 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)₄.

Chromium and Fe formed -(Fe_1-xCr_x)OOH compound with nanoparticle size, therefore had stabilized rust layer covering on WS matrix.

Rare earth metals (about 2 kg/t) increased pH in electrochemical area and passively formed phosphide layers clingging and covering on the surface, thereby improved corrosion resistance.