Influence of acetylenic derivatives on corrosion of chromium and chromium containing steels in hot acid solutions

The influence exerted by some acetylenic alcohols (1-octyne-3-ol (OCT), 3-methyl-1-butyne-3-ol (MET), and 1-iodo-3-methyl-1-butyne-3-ol (IOD)) on the corrosion of chromium in a 1N HCl solution at 70 degrees C has been evaluated by electrochemical impedance spectroscopy (EIS) measurements and polarisation curve determinations. These compounds care poor inhibitors of the dissolution of chromium in acid despite the positive benefits obtained for other transition metals such as iron or nickel. Only OCT, at a 10 mM concentration, displays a highly protective action but this decreases rapidly during the first two hours of testing. Even the inclusion of modest amounts of chromium in iron alloys is sufficient to reduce the inhibitive effect of acetylenic alcohols. For instance, the protective action of OCT is high and persistent only for plain steel, and it decreases rapidly for alloys with chromium contents of 5-17%. The negative influence of dissolved Cr3+ ions has also been demonstrated, since their presence causes a reduction in the inhibiting efficiency of OCT on both plain and chromium containing steels.