| 摘要 |
PURPOSE:To carry out concn. control of an oxidizing agent at a low cost by automatically and quantitatively determining the oxidizing agent in a phosphate chemical conversion treatment liquid by a electrochemical means to control so as to always maintain a concn. of said oxidizing agent at a definite value. CONSTITUTION:As an oxidizing agent, sodium nitrite, sodium chlorate or hydrogen peroxide is used and a concn. thereof is 1% or below, generally, 10-1,000ppm. A part of a phosphate treatment liquid to be controlled is introduced into an electrolytic tank and again returned to continuously recirculate said liqud in a constant liquid amount and a temp. of the electrolytic tank is adjusted to 10-80 deg.C and a pH of an electrolyte is maintained to 2-4. Into the electrolytic tank, two electrodes and a reference electrode are immersed and a constant voltage of -400-+1,200mV is applied on the basis of an silver chloride electrode. In proportion thereto, electric current is passed but an oxidizing agent pouring apparatus is cooperated with an electric current controller so as to maintain an electric current value definitely and a concn. of the oxidizing agent is automatically controlled by starting and stopping the pouring apparatus. |
