Corrosion protection of stainless steel by a new and low‐cost organic coating obtained from cashew nutshell liquid

Abstract

AbstractIn this work, the corrosion protection of 316L steel was promoted by an electro‐synthesized polymer obtained from the technical cashew nutshell liquid (t‐CNSL). Spectroscopic techniques confirmed the polymer formation. The polymer was dispersed in the ethyl acetate solvent and used to form coatings on 316L steel substrates. The coated samples were subjected to electrochemical tests in a saline environment. The coated electrode with poly(t‐CNSL) polymer was exposed to the corrosive medium for 24 days, and superior corrosion protection was observed compared with the uncoated sample. The open circuit potential measurements showed that the coated sample possessed a more positive corrosion potential when compared with the uncoated substrate. The electrochemical impedance spectroscopy results indicated that the coated electrode's polarization resistance (Rp) recorded ~1.0 MΩ cm2 after 24 days of exposure. A decrease in polarization resistance was observed with the exposure time due to the presence of micropores in the t‐CNSL coating. The polarization curves exhibited that the coated electrode with poly(t‐CNSL) has lower corrosion current density and less negative corrosion potential than the uncoated steel electrode. Therefore, t‐CNSL favors the manufacture of thin poly(t‐CNSL) coatings for corrosion protection purposes besides being a low‐cost material.