The influence of carbon monoxide, ethylene, acetylene, allyl alcohol and propargyl alcohol on nickel electrodissolution in aqueous 0.5 M H2SO4 was Studied after the adsorption equilibrium of each of these species at a fixed potential and room temperature had been attained, The hindrance of nickel electrodissolution by carbon monoxide is greater than that resulting from double and triple C-C bond compounds at the same concentration in the solution, Corrosion current, corrosion potential, the amount of dissolved nickel at a constant potential and steady hydrogen evolution polarization data combined with voltammetric deconvolution data provide information about the nickel electrodissolution inhibition capability of these substances in acid solution.