CORROSION RESEARCH ROUND‐UP

Fe‐Ni‐Cr Electrolytic coating. The resistance to corrosion of the ternary Fe‐Ni‐Cr alloy is of increasing practical interest (as well as theoretical). In the present case an electrolyte was prepared for depositing this alloy as used in the constitution of stainless steel, Russian mark 1Kh18N9T, or closely approximating thereto. The best results as to stability of electrolyte were obtained with anodes of this steel. Optimum current density at 25° was 15 to 16 amp./sq.dm., and at 40° 18 to 20 amp./sq.dm., the pH being 1.6 to 1.8. Using a diaphragm in the tank it was found that the catholyte becomes alkaline. By due adjustment with salts and keeping the pH at 1.6 to 1.8 good reproducible results were obtained. Current yield did not exceed 18%. Optimum c.d. at 25° to 30° was 10 to 15 amp./sq.dm. If the coatings exceeded 6 µ in thickness there was poor adhesion with the base metal. This improved after heat treatment. In microhardness the coatings were about the same as the alloy. Their corrosion resistance was tested in 5% H2SO4 and shown to be of high order, but due to small cracks in the coating there was solution of the base metal and the coating tended to peel off. Eight references.—P. F. Kalyuzhnaya et al. (Zh. prikl. Khim., 1962, (5), 1057–1065). See also article on the effect of hydrogen sulphide on the electrode potential of stainless steels (Ibid., 1065–1070); 19 references.