Abstract
The adsorption of 4‐ethylpyridine, 4‐ethylpiperidine, and very low molecular weight poly (4‐vinylpyridines) was studied in cyclohexane solutions containing hydrogen reduced steel powder. Isotherms were obtained for the monomers at 30°C. They show that an amount equivalent to monolayer formation is adsorbed at equilibrium concentrations in the range 
. The polymer was adsorbed to a much greater extent. Using a specially designed chromatographic method, the heat of adsorption of the piperidine derivative from cyclohexane was determined. Simultaneous measurements of the adsorption of the polymer and the corrosion of the steel in aqueous hydrochloric acid have shown that the corrosion rate decreases by 80% as the polymer adsorbs to form a very incomplete layer. From these results, it is concluded that these compounds chemisorb to the steel surface and that the 4‐ethylpiperidine is bonded at the nitrogen atom but that the 4‐ethylpyridine is adsorbed in a position with the plane of the ring parallel to the steel surface. Attachment of polymer is at multiple sites in the molecule, but appreciable portions of the chains are left in the solution phase. The area which is deactivated toward corrosion by adsorption of poly (4‐vinylpyridine) from 
is considerably greater in extent than that which is physically covered by the adsorbed molecules, i.e., a large neighboring area of steel surface is ennobled by the adsorbed polymer molecules.