The dezincification of brass and its inhibition in acidic chloride and sulphate solutions

The dezincification of 60 40 brass has been studied in acidic chloride and sulphate solutions under accelerated experimental conditions using weight loss and potential measurement techniques. A particular variation of potential with immersion time was observed to be the characteristic feature of dezincification. The results obtained support substantially the operation of both selective dissolution of zinc and simultaneous dissolution of copper and zinc followed by redeposition of copper, alternatively with time, during dezincification. The effect of surface active compounds such as thiourea, thioglycolic acid, thioglycol and halo-acetic acids on dezincification of brass has been discussed on the basis of models proposed for synergistic effects of organic molecules and anions involved in the medium. © 1987

EFFECT OF THIOUREAS ON CORROSION OF BRASS IN NITRIC ACID.

The corrosion behavior of brass (60/40) in nitric acid containing thiourea and its N-substituted derivatives such as allylthiourea, methylthiourea, dimethylthiourea, phenylthiourea and diphenylthiourea, has been investigated using weightloss and polarization techniques. The inhibitor efficiency of each addition agent was found to depend on a) the concentration of nitric acid, b) temperature of the medium c) stirring rate of the solution and d) the nature of the inhibitor and its concentration. Two distinct mechanisms based on the concentration of HNO//3 are proposed to account for the mode of inhibitor action

Benzoic acid and substituted benzoic acids as interfacial corrosion inhibitors for copper in HClO4

Corrosion of copper in HClO4 solution containing various concentrations (10-7-10-4 M) of benzoic acid, p-toluic acid, p-nitrobenzoic acid, phthalic acid and terephthalic acid has been studied at 30° C. These compounds inhibit corrosion effectively even in trace concentration. The corrosion rate is a function of temperature,concentration and nature of the inhibitor. The inhibitor efficiency calculated from weight loss and polarization methods are in good agreement. Thermodynamic parameters foradsorption of inhibitors have been evaluated by using the Bockris-Swinkels adsorption isotherm with n=5 as the configurational function. The corrosion inhibition is discussed from a view point of adsorption of inhibitor molecules at the metal-solution interface. © 1981 Chapman and Hall Ltd

The effect of thiocyanate ions on the corrosion of copper in perchloric acid

The effect of thiocyanate ions on the corrosion of copper in 0.1 M HClO4 was investigated in the presence of various concentrations of thiocyanate ions using weight loss and polarization methods. The corrosion rate decreased markedly in the presence of thiocyanate ions and maximum percentage protection (93.7%) was obtained at 10-3 M thiocyanate ions. The drift of the corrosion potential in the less noble direction and the increase in the anodic Tafel slope are consistent with the inhibition by thiocyanate ions of both the anodic and the cathodic reactions of the corrosion process. The variation in the corrosion rate with the concentration of thiocyanate ions is attributed to the specific adsorption of thiocyanate ions and precipitation of cuprous thiocyanate on the copper surface. © 1980