Hideo Sugawara

Dezincification of brass

Dezincification of copper-zinc alloys has been studied by means of a potentiostat and an electron probe micro-analyser. The electrochemical behaviour of α and α + β phase brasses are essentially similar to those of copper in a 3% NaCl aqueous solution. The corrosion potential of copper-zinc alloys becomes less noble with increasing zinc content. The surface film consisting of Cu2O or CuCl is formed in the early stage of corrosion and a complex potential distribution is shown in the surface films and the matrix. The dissolution rates of brass are accelerated by the complex potential distribution, leading to dezincification. The process of dezincification is considered to be the redeposition of copper.

Effect of Prestrain on Stress Corrosion Cracking of Type 304 Stainless Steel by Means of the Stress Relaxation Method

Abstract The relationship between the susceptibility of stress corrosion cracking (SCC) and the amount of deformation structures in Type 304 stainless steel in an H2SO4/NaCI solution system at room temperature was investigated by means of the stress relaxation method. SCC was observed in the prestrained specimens, whereas no cracking occurred in specimens without prestraining. The number of cracks was affected by the amount of deformation structures, which varied according to the annealing temperature after prestraining or according to the prestraining temperature. The results of magnetic measurements on the prestrained specimens as a function of the annealing temperature showed that the cracking region was in good agreement with the range of existence of strain induced α-martensites. Transmission electron microscope observation showed that ϵ- and α-martensites formed by prestraining at temperatures below 413 K (140 C) dissolved in preference to the austenite matrix. A strain induced martensite in Type 30...