INHIBITION-MECHANISM OF CARBON-STEEL IN NEUTRAL SOLUTIONS BY N-PHOSPHONO-METHYL-GLYCINE

Corrosion inhibition of carbon steel in neutral aqueous solutions by N -phosphono-methylglycine (NPMG) is based mainly on the formation of an inhibiting film that protects the base metal. In order to understand the structure and composition, the layers formed on carbon steel were sputtered by an argon beam to obtain a depth profile using Auger elect ron spectroscopy (AES). The influence of changes in the water composit ion using model solutions (with and without calcium) in contact with c arbon steel on the formation and growth rate of the film was studied. In addition, the effect of several factors such as time of contact and the addition of some cations, such as Ca2+ and Zn2+, on the formation and composition of the inhibiting films was investigated. In addition to surface analysis, weight loss method was used to optimize and char acterize the inhibitor efficiency and the effect of synergism.