Accelerater of Steel Oxidation in Ammonium Nitrate Solutions

The effect of adding the amide-type URMP-4 accelerater of the growth of magnetite coatings (MCs) in 2.5% NH4NO3 on the corrosion resistance of oxidated low-carbon steel is studied. Corrosion and electrochemical data indicate that URMP-4, unlike other acceleraters, not only increases the thickness of an MC but also enhances its protective properties. Subsequent passivation of such a coating reduces corrosion losses six to seven times. A two-step process of the MC formation is proposed. At the first step, URMP-4 inhibits steel dissolution by facilitating the electrochemical formation of magnetite at steel by the reaction 3Fe + 4H2O = Fe3O4 + 8H+ + 8e. At the second step, an MC grows thicker according to the deposition mechanism.