Metallic surface can be protected with the chemisorbed film of high molecular weight organic corrosion inhibitors.
The film may be formed at the definite temperature and may desorb at the definite temperature. It is reported that the desorption will take place at the temperature when filming substances are added in lubricants.
In this study, acetoacetic acid ester is hydrogenated with filmed Ni-catalysts in an autoclave. From the starting temperature of the reaction and analysis of the reaction products, the desorption temperature will be obtainable. Cetyl amine departs from the catalysts at 100°C, palmitic acid amide at 130°C and cetyl mercaptan at 170°C.
While amine-filmed catalysts are prepared from its alcoholic solution and acid amide from its dioxane solution at room temperature, cetyl mercaptan can be absorbed only at over 70°C. Then, cetyl mercaptan-filmed catalysts are prepared by dipping the catalysts in the boiling alcoholic solution of cetyl mercaptan. This temperature of adsorption is pre-determined by measuring the current density between Cu and Fe electrodes in 3% NaCl aqueous solution. The Cu electrode is preliminarily treated with dilute alcoholic solution of the mercaptan at various temperatures.
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