In the previous report, it has been made to evaluate the corrosion inhibiting effects of three-component inhibitor for mild steel in HCl. Even at low concentration of the inhibitor, it showed the inhibiting effect of higher than 99%.
In this study, we have investigated in detail the inhibiting effects of the inhibitor and have studied the corrosion inhibiting mechanism. The results were as follows:
(1) When other metal ions, such as Mg
2+, Ca
2+, Zn
2+, Cd
2+, Mn
2+, Ni
2+, Ag
+ and Pt
4+, were used instead of Cu
2+, high inhibiting effects was not obtained by these inhibitors.
(2) One of the three components, thiourea, was used for Cu
2+-chelate agents and the chelate compound played an important role upon inhibiting effects. Thiourea derivatives were able to be substituted for thiourea, but cupferon and organic acids were not.
(3) An effective inhibitor was also made from the combination of Cu
2+, thiourea and formaldehyde.
(4) From measurements of the polarization curves, it was assumed that the cathode reaction was mainly retarded by the Cu
2+-thiourea complex and the anode reaction by the urotropine. Therefore, high inhibiting effect may be obtained by this inhibitor.
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