スルファミン酸による金属の腐食とその防食 (その2)

抄録

In the previous report, it has been made to evaluate the corrosion rate of steel and other metals in sulfamic acid solution and to search for the corrosion inhibitor for steel in this solution. Resulting from these tests, thiourea derivatives and acetylenic compounds were found to be most effective inhibitors.
In this study, we have investigated in detail the inhibiting effect of these inhibitors for iron and other metals in various corrosive environments of sulfamic acid solution. The results were as follows:
(1) Ca⁺⁺ ion has no influence on the corrosion of steel and the effect of inhibitors.
(2) An increase in amount of Fe⁺⁺⁺ ion results increase in the corrosion rate and decrease in the effect of the inhibitors.
(3) Inhibiting effect on cast iron is the nearly same as that on steel, although the corrosion rate of the former is greater than that of the latter.
(4) The corrosion of Cu, Al, and Cu-Zn alloy in sulfamic acid in the presence or absence of the inhibitors is smaller than that of steel.
(5) The effect of the inhibitors for steel is not lowered by recycled run of the same solution (5 times), but it is slightly lowered by aeration.
(6) The synergistic effect of some surface active agents on the inhibiting effect of 1, 3-diethyl-thiourea for steel is observed only in inhibitor concentration of below 0.2m mol/l.