Application of thin layer activation technique for studying corrosion inhibition in steel

Stainless steel (SS304L) and carbon steel (CS) are widely used in different components of plant and transport lines in oil refineries. These steels are prone to corrosion in presence of organic acids, inorganic sulphides and as a result of fluid flow. Hence corrosion control by means of suitable inhibitor is an important area of research. Organic molecules containing amine group are reported to be used for inhibition of corrosion of mild steel. Thin layer activation analysis (TLA) is useful for studying corrosion, erosion and wear processes in metallic and alloy components. In the present study the inhibition effect of hexamethylenetetramine (HMTA) on acid corrosion of SS304L and CS are investigated. 13 MeV proton beam from Pelletron accelerator was used for surface activation of SS304L and CS coupons for use in TLA technique. NaI(Tl) scintillation detector assembled with multichannel analyzer was used for monitoring loss in activity with time as a measure of corrosion rate. Organic molecule acts as corrosion inhibitors by adsorption at the metal-solution interface. The inhibition property is associated with two processes, i.e, the adsorbed organic molecules block the reaction sites on metal surface and they generate a physical barrier to reduce the diffusion of corrosive species to the metal surface. The corrosion rate was monitored in presence of different concentration of HMTA (0-1000 ppm) in both the cases. As CS is more corrosive as compared to SS304L the inhibition effect of HMTA is different in these two materials. The result showed that inhibition effect of HMTA is more pronounced in case carbon steel than SS304L. (author)