Corrosion Inhibition of Type 430 Stainless Steel in HCl Solution by Dipyridinium Salts

The inhibitive actions of three sensitized derivatives of n,n'-diquaternized 4,4'-dipyridinium salts (tmdpybr2, hmdpybr2 and mphdpycl2) on general and pitting corrosion of 430 stainless steel (ss) in aerated 0.1m hcl have been studied at different temperatures. corrosion potential and polarization measurements proved that the three compounds act as mixed type inhibitors with dominant anodic and their adsorption on the steel surface obey langmuir adsorption isotherm. the diquaternized salts inhibited the corrosion and improved the passivation of the ss, their inhibition efficiencies (except for tmdpybr2) increased with temperature. the mechanism of corrosion inhibition was discussed in the light of the molecular structure of the dipyridinium salts.