Abstract
On the bell-annealed hot rolled strip and the bright-annealed cold rolled strip of commercially arc-melted and processed 17% chromium stainless steel, the effects of aluminium content and composition of non-metallic inclusion on the susceptibility to rust corrosion during the 5% NaCl salt spray test have been investigated.
The optical and scanning electron microscopic observations and electron probe micro-analyses of the specimens after a few minutes of the salt spray test show that pitting corrosion initiates due to the dissolution of calcium-rich sulphides which are located as shells surrounding the aluminate inclusions. Iron dissolves from inner surface of a pit and deposits as ring-like rust around the pit.Segregations of calcium and sulphur are detected at this ring-like rust.
The proportion of the number of these water-soluble inclusions increases with the aluminium content of steel.
