Synergistic Effects of Inorganic and Organic Cations on Inhibitive Performance of Propargyl Alcohol on Steel Dissolution in Boiling Hydrochloric Acid Solution

The role of different inorganic cations of several elements and organic materials in combination with different concentrations of propargyl alcohol (PA) was investigated in an effort to control the dissolution of mild steel in boiling (102 ± 1°C) hydrochloric acid (HCl) solution. Inorganic cations of chromium (Cr⁶⁺), arsenic (As³⁺), tin (Sn²⁺), copper (Cu²⁺), nickel (Ni²⁺), and mercury (Hg²⁺) were studied. Organic materials studied included phenol, formaldehyde, O-aminobenzoic acid, sodium hypophosphide, and hydroquinone. Cr⁶⁺, As³⁺, and Ni²⁺ provided higher synergism, followed by Cu²⁺, Sn²⁺, and Hg²⁺. Phenol and formaldehyde provided higher beneficial effect. Except for phenol and formaldehyde, the other organics stimulated corrosion when added at higher concentrations. Organic additives were more effective than inorganic cations. Cu²⁺, Cr⁶⁺, and Ni²⁺ accelerated corrosion when used without PA but strongly reduced dissolution in its presence. As³⁺ reduced the corrosion rate alone and in combination with PA. Open-circuit potential measurements and polarization studies indicated PA controlled the corrosion rate by formation of a surface layer at the interface. Its effect was enhanced if another specie was present in the solution that promoted the film formation.