To the problems of the function and the spreading of sulphate nests in the layer of corrosion products on steel

Abstract

AbstractThe formation and propagation of sulphate nests in the corrosion products formed during atmospheric corrosion of steel is controlled to a large extend by the osmotic pressure within these nests. The same importance can be attributed to the composition of the FeOOH containing film covering the nests; as the FeOOH content increases the elasticity of the film is increased, too, so that the membrane is able to remain intact, i.e. without cracking even at increasing osmotic pressures in the nest. This behaviour improves the resistance of steel to atmospheric corrosion. These conditions are very important in particular with periodic wetting regimes. This mechanism also explains the effect of silicon which is incorporated in amorphous form in the corrosion products and thus improves the elasticity of the corrosion product membrane.