The effect of cationic surfactants in acid cleaning solutions on protective performance and adhesion strength of the subsequent polyurethane coating

The subsequent effect of the use of monomeric cationic surfactants, dodecyltrimethylammonium bromide (DTAB) and its gemini counterpart, 12-4-12, in 1 M sulfamic acid cleaning solution on the corrosion resistance and adhesion strength of polyurethane coating on mild steel surface was studied by salt spray and pull off, respectively. The EIS (electrochemical impedance spectroscopy) was employed to evaluate the corrosion behavior of mild steel during the contact with sulfamic acid solutions. Inhibition performance of DTAB on mild steel at the initial period of immersion was somewhat higher than 12-4-12, while at prolonged immersion period 12-4-12 was more effective than DTAB. The higher protection and adhesion for the coating applied on the mild steel washed with DTAB solution was connected to more rapid adsorption for DTAB than 12-4-12 at short immersion period due to its small molecular weight which resulted in better mobility of DTAB molecules.