CORROSION BEHAVIOR OF CARBON STEEL WITH HMTA INHIBITOR IN PICKLING PROCESS

In this investigation, attempts have been made to study the inhibitive effect of hexamethylenetetramine (HMTA) on carbon steel in 10% HCl (mass%) by weight loss, potentiodynamic polarization, EIS, and AFM. Results indicate that inhibition efficiency (IE) of HMTA increases with the increase in pickling immersion time from 10 to 60 min, and IE also increases with the increase in temperature. At higher temperatures (80°C), the IE values are higher and almost independent of pickling time. HMTA can be adsorbed on the surface of metal and reduce the corrosion rate of metal. HMTA is a kind of mixed inhibitor and can retard both the anodic dissolution and cathodic hydrogen evolution reactions independently. IE increases with the concentration of HMTA. Electrochemistry measurement shows that adsorption follows the Langmuir isotherm and the value of free energies of adsorption (ΔG_ads) is < 0, so the adsorption process can occur automatically. AFM analyses show HMTA can affect the surface roughness and protect metal.