The mechanisms through which organic compounds bond to steel substrates are investigated using infrared reflection absorption spectroscopy (IRRAS). Ester groups form hydrogen bonds already at room temperature. No chemical reaction, such as hydrolysis of ester groups, takes place, even at high temperatures. Exposure of polyester-coated steel to a diluted acetic acid solution in methanol leads to chemisorption of acetic acid as evidenced from IRRAS despite the presence of hydrogen-bonded PETG ester groups. A number of polymers containing acidic side-groups were applied to steel with the aim to investigate the adsorption mechanism of these polymers. The polymers were found to chemisorb, forming carboxylate, phosphonate, sulfonate and phenolate salts.