Indole-3-carbaldehyde and 2-methylindole as corrosion inhibitors of mild steel during pickling. Issue 5 (7th September 2015)

• Record Type: Journal Article
• Authors: Ashhari, Shabnam; Sarabi, Ali Asghar
• Is Part Of: Pigment & resin technology. Volume 44:Issue 5(2015)
• Page Start: 322
• Page End: 329
• Publication Date: 2015-09-07
• Subjects: Protective coatings -- Periodicals; 667.62305
• DOI: 10.1108/PRT-11-2014-0104
• Languages: English
• ISSNs: 0369-9420

Abstract

<abstract> <title> <x content-type="archive" xml:space="preserve">Abstract</x> </title> <sec> <title content-type="abstract-heading">Purpose</title> <p> – This paper aims to investigate the corrosion inhibition effects of indole-3-carbaldehyde and 2-methylindole on mild steel in 1 M HCl solution. </p> </sec> <sec> <title content-type="abstract-heading">Design/methodology/approach</title> <p> – Indole-3-carbaldehyde and 2-methylindole as corrosion inhibitors of mild steel in 1 M HCl solution were investigated by polarisation and electrochemical impedance spectroscopy (EIS). Adsorption isotherm and mechanism were calculated. Quantum chemical calculations were used to find out a correlation between electronic structure of inhibitors and inhibition efficiency. Changes in the properties of metal surface in HCl solution in the presence of inhibitors were studied by contact angle measurements. </p> </sec> <sec> <title content-type="abstract-heading">Findings</title> <p> – Polarisation results revealed inhibitors could reduce cathodic and anodic reactions rates on metal surface. EIS analysis showed that inhibition efficiency of indoles increases by increasing the inhibitors' concentration; maximum inhibition efficiency was 95 and 94 per cent in solutions containing 1 mM indole-3-carbaldehyde and 2-methylindole, respectively. Inhibitors' adsorptions on metal surface were confirmed by analysing the exposed metals' surface through contact angles measurements. The adsorption of inhibitors was found to follow Langmuir isotherm. Quantum chemical calculations showed that a more positively charged benzene ring in the structure of two indole-based inhibitors would lead to higher adsorption to metal. </p> </sec> <sec> <title content-type="abstract-heading">Originality/value</title> <p> – This research was carried out to understand the effects of two different functional groups (-C=O, -CH3) with different induction effects on the indole structure and on inhibition efficiency of corrosion inhibitors with the purpose of using these components in industrial application as acid wash solutions to etch and remove rusts from metal surfaces.</p> </sec> </abstract>