溶融亞鉛メッキ層中の塩化物の定量およびその含有量と腐食との関係について

Abstract

By photometric method of analysis, the author determined the chemical composition of the coating with reference to its contained chloride by adding 3N-HNO3 as oxidizing agent for Fe.. to the stripping solution of 3N-H2SO4, changing Cl′ in the solution into hydrosol of AgCl with 0.1% AgNO3.The results obtained were as follows:(1) Cl-content in the coating produced by Dry Golvanizing Method of washing with hot flux solution such as 5N-NH4Cl or 5N-ZnCl2·NH4Cl was about 0.01% by weight and with 5N-ZnCl2 was about 0.03%.Conditions of this experiment were as follows:Material used was 0.6C steel wire, composition of bath electrolytic zinc, temperature of Zinc bath 450°C, and dipping time 1-2min; hand dipping process being used.(2) When produced by washing with cold flux solution such as 5N-HCl, 5N-NH4Cl or 5N-ZnCl2, Cl-content was 0.08-0.10%.Conditions of this experiment were as follows:Material used was black heart malleable iron, and other conditions were the same as the above.(3) Cl-content in the coating produced by Wet Galvanizing Method, of using machine and washing with Pb-Zn bath was also 0.01-0.10%. The longer the dipping time in Pb-bath was the less was the Cl-content in the coating.Conditions of this experiment were as follows:Specimens used in these experiments were the product of certain factories. Material used was 0.1C sheet, composition of Zinc bath, spelter with 0.1-0.2% Sn and 0.1% Sb, temperature of Zinc bath 450°C±10°C, temperature of Pb-bath 480°C, and dipping time in Pb-bath 7-18sec.