Investigation of the anodic behavior of nickel in H2SO4 solutions using galvanostatic polarization technique. III. Inhibition of pitting corrosion using nitrogen-containing organic compounds
Arej S. Al-Gorair, S. Abd El Wanees, H. Hawsawi, Mahmoud G. A. Saleh, M. Abdallah
Abstract
ABSTRACT Thiourea, (Inh I), N-allylthiourea, (Inh II), and 3-allyl-1-[(2-methoxyphenyl)methyl]thiourea (Inh III) were used to mitigate the pitting corrosion of Ni in 0.01 M H 2 SO 4 by the galvanostatic polarization technique. The used compounds decrease the pitting corrosion by displacement of the pitting potential, E pit into more positive values, with decreasing the amount of electricity, Q inh , required to reach E pit . The inhibition efficacy, η, was found to increase with raising the inhibitor concentration and depend on its kind. The inhibition efficacy, η, increases in the sequence Inh I < Inh II < Inh III. The inhibitive action of these compounds is discussed in terms of blocking the electrode surface through an adsorption process following the Temkin isotherm. The calculated values of ∆G a ° ds are found to be –48.63, –50.18, and –51.84 kJ/mol for Inh I, Inh II, and Inh III, successively. These values are compatible with a chemisorption process including the transfer of electrons from the inhibitor molecule to the Ni metal surface.