酸洗浄時における異種金属接触系の腐食について

抄録

In the previous report, it has been revealed that the acid attack on copper alloys during acid cleaning is mainly accelerated by oxidizing ions such as ferric or cupric ion in the inhibited hydrochloric acid solutions.
In the case of coupling dissimilar metals, there is the possibility of attack caused by galvanic action. When coupled, the anodic metal will corrode faster and afford some protection to the other.
In this study, we have investigated the effects of inhibitor, gas atmosphere and oxidizing ions such as ferric or cupric ion on the corrosion of steel-copper alloy couple in hydrochloric acid solution.
The results obtained are as follows.
(1) The greater the corrodibility of hydrochloric acid is, the higher the effect of galvanic action on the corrosion of steel-copper alloy couple is.
In the noninhibited hydrochloric acid solution containing oxidizing ions, the corrosion rate of steel coupled to copper alloy is greater than that of uncoupled steel and much greater when air is bubbled through the solution.
(2) But, in the inhibited hydrochloric acid solution, the effect of galvanic action is decreased, and the corrosion rates of coupled steel and copper alloy, whether in the presence of oxidizing ions or not, are approximately the same as those for uncoupled steel and copper alloy.
(3) Also, it has been verified that the cathodic protection is very effective for prevention of acid attack on such galvanic couples as steel-stainless steel system and steel-copper alloy system, in the same way as it is effective in the case uncoupled steel.