Role of hydrogen promoters on corrosion and hydrogenation of mild-steel in aqueous and methanolic hydrochloric-acid solutions

Corrosion and hydrogenation of mild steel (MS) in aqueous and methanolic solutions of hydrochloric acid (HCl) were studied using weight loss, electrochemical, and hydrogen estimation methods. The effects of some hydrogen-promoting species such as cathodic poisons (i.e., sodium arsenite [NaAsO2], selenium dioxide [SeO2], stannous chloride [SnCl2], and mercuric chloride [HgCl2]) were investigated to understand their role on the dissolution and hydrogen absorption characteristics of MS in aqueous and methanolic HCl solutions. The dissolution rate of MS in methanolic solution of HCl was considerably higher than in the aqueous HCl solution, where as the hydrogen pickup values of the steel in methanolic solution were less than in the aqueous HCL solution. Addition of NaAsO2 lowered the dissolution rate and hydrogen pickup value in both solutions. The other poisons had specific effects on the dissolution rate and hydrogen pickup values.