Effect of (R+, X–) salts addition on nickel corrosion in 1M sulfuric acid medium

Abstract

AbstractWe used the electrochemical techniques to study the effect of the addition of four salts, K+,Cl−, K+,Br−, K+,I− and C8H17Ph3P+,I−, on the corrosion behaviour of nickel when submitted to 1M sulphuric acid medium. After one hour of immersion time, we noted an acceleration of nickel corrosion process after the addition of K+,Cl− and K+,Br− in the 1M H2SO4 electrolyte. K+,I− exhibited an inhibition of the anodic Ni corrosion process whereas the phosphonium iodine (R+,I−) acts simultaneously on both processes: it is a mixed inhibitor. Such result is due to the adsorption of the alkyl group C8H17 which limited oxygen diffusion.EIS characterization of Ni exhibited surfaces after iodine salts addition allowed us simulating the resulting interfaces by electrical equivalent circuits. We concluded that (K+,I−) addition decreased the material corrosion rate without changing the alteration mechanism. That result is due to the formation of NiI at the electrode surface. On the other hand, phosphonium iodine addition modifies the interface behaviour. In fact, the alkyl part of the organic iodine adsorbs at the surface preserving it against the corrosive action of the sulfuric acid.