The efficiency of trimethylamon iodide as a corrosion inhibitor for welded joint of duplex stainless steel UNS S31803

Duplex stainless steel owns its denomination to the combination of two types of phases, ferritic and austenitic, whose main characteristic is the excellent resistance to corrosion in aggressive media due to its ability to form a passive layer. Because it has this characteristic, this material is mainly used in the petrochemical industries. This article studied the efficiency of the (3-indolimethyl) trimethylammonium iodide (DIMTI) ionic liquid, as a corrosion inhibitor in 1 M solution of hydrochloric acid (HCl) for UNS S31803 duplex stainless steel welded, and heat treated. The corrosive process was investigated by potentiodynamic polarization test. The samples were evaluated in the presence of 1 M HCl solution and with DIMTI ionic liquid at a concentration of 0.4 and 0.8 mM. The samples subjected to this corrosive medium obtained excellent rates of corrosion inhibition, of 87 and 94%, respectively. Based polarization curves, it was found that the DIMTI, ionic liquid acted as a mixed type of corrosion inhibitor. The inhibition efficiency increased with the increase in concentration, confirming its adsorption on the surface of the metal. With the present study it was concluded that ionic liquids are a green and sustainable alternative to replace traditional toxic corrosion inhibitors.