It has been found that salts of amines and C₁₈ unsaturated acids act in a different manner as corrosion inhibitors in organic coatings, depending on the reaction of the corrosive environment. The salts showed outstanding inhibition in an acidic environment. Comparably high inhibition was obtained with these compounds through acidification of the coating material, followed by exposure to a neutral solution. It was also found that the mode of protection by inhibited coatings may be identified by determining the impedance of coated electrodes as a function of the frequency of the low voltage measuring signal. -- AATA