Hydroxamic acid corrosion inhibitor for steel in aqueous solution

The selected dihydroxamic acid derivatives, namely oxalyl-dihydroxamic acid (C2) and pimeloyl-1,5-di-hydroxamic acid (C7) have been synthesized and evaluated as corrosion inhibitors for carbon steel in neutral aqueous solution by potentiodynamic polarization and ac impedance methods. C2 molecule acts as good inhibitor with inhibition efficiency value reached 91%; it is well adsorbed most likely throughout the two hydrophilic groups, and forms a protective film on the metal surface. C7 has moderate inhibition efficiency probably due to the presence of lone, single hydrocarbon chain in the molecule, negatively affect the adsorption process. Addition of Ni2+ to C7 significantly improve the inhibition efficiency, throughout the formation of a dense compact layer of complexes between Ni2+ and C7.