The inhibitive effects of 8-mercaptoquinoline and its iron chelate complex in the acid corrosion of iron in 1 M HCl

Abstract

The inhibitive effect of a 8-hydroxyquinoline derivative (1) and the corresponding Fe 2+ chelate (2) in the corrosion of Fe in 1 M HCl was studied. The adsorption mechanism of these compounds was considered and the post-treatment effect of these compounds was studied. An increase in the concentration of compounds 1 and 2 increases corrosion inhibition for all the compounds studied. The residual protective effect of chelates is much higher than that of the corresponding ligands. The results that we obtained were interpreted in terms of organic compounds -metal surface interactions. Key words: corrosion, inhibitor, iron, chelates, residual protective effect.Received: June 26, 2014June 26, . doi: 10.17675/2305June 26, -6894-2014 The use of metal chelates as corrosion inhibitors is very promising because they are usually poorly soluble, highly adsorbable, and have high coverage capacity due to the formation of a chelate structure containing several molecules of the original inhibitor as ligands. These factors enhance the inhibitive properties of the complex and strengthen the complex-metal surface bonds. The latter factor should also prolong the post-treatment effect (residual protective effect of the inhibitor) when a pre-inhibited metal is transferred to a noninhibited corrosive environment [1,2]. Earlier, 8-mercaptoquinoline derivatives were tested as inhibitors of the acid corrosion of some metals. Their inhibitive effect is associated with the formation of insoluble chelate complexes between the corrosion products of metals (Fe, Cu, cast iron, etc.) and the 8-mercaptoquinoline molecules that cover the surface of a corroding metal, thus preventing access to the corrosive environment [3,4]. We found it interesting to compare the protection mechanisms of 8-mercaptoquinoline itself and its chelate complex with a corroding metal. In the latter case, the chelate used as an inhibitor is a preformed complex (in contrast to previous tests where a chelate complex was formed during metal corrosion). ExperimentalCorrosion tests were carried out using iron band specimens (11.25 cm) containing the following impurities, %: P 0.035; C 0.12; S 0.045; Cr 0.15; Ni 0.2; Mn 0.45; Si 0.005; Mg 0.05.

Laboratory assessment of tetrakis(hydroxymethyl)phosphonium sulfate as dissolver for scales formed in sour gas wells

“…Alternative dissolvers are high desirable for downhole applications due to drawbacks associated with commonly used HCl acid dissolvers [20]. The aggressive nature of HCl acid can cause severe corrosion to downhole tubular at elevated temperatures [21][22][23][24]. Dissolution reaction produces high concentration of toxic H 2 S gas in low pH solutions.…”