An atomic emission spectroelectrochemical study of corrosion inhibition: The effect of hexamethylenetetramine on the reaction of mild steel in HCl

Research highlights: → Time resolved elemental dissolution rates on time scales typical for pickling lines. → Segregated impurities dissolve selectively at early stages. → At high HMTA concentration the dissolution rate is the same for different steels. → Several mechanisms of HMTA inhibition are discussed. - Abstract: The dissolution of low carbon steel in hydrochloric acid has been investigated by atomic emission spectroelectrochemistry. The rate of Mn, Fe and P dissolution was measured as a function of time for steels of variable Mn and P composition and as a function of HMTA concentration. Regardless of the reactivity of the steel in uninhibited solutions, at high concentration of HMTA, all steel grades show a nearly identical dissolution rate. The effect is selective for Fe; the dissolution of segregated Mn is not affected by HMTA.