The influence of deanol on the corrosion behaviour of mild steel in dilute sulphuric acid with sodium chloride addition was studied by means of mass-loss, potentiodynamic polarization, electrode potential monitoring, scanning electron microscopy and statistical analysis. Results show that deanol performed excellently with a maximum inhibition efficiency of 97.9 % obtained from the mass loss technique and 98.23 % from the potentiodynamic polarization tests at the maximum deanol concentration evaluated. Polarization studies show that the amino alcohol is a cathodic type inhibitor. Adsorption of deanol on the steel surface was observed to obey the Langmuir and Frumkin adsorption isotherms. Scanning electron microscopy studies confirmed the corrosion protection property of deanol to be through adsorption on the mild steel surface while statistical evaluation showed the overwhelming influence and significance of inhibitor concentration on inhibition efficiency compared with exposure time.
KEYWORDSOrganic compounds, metals, deanol, corrosion, sulphuric acid, inhibitor
IntroductionMild steel has excellent mechanical properties. Its low cost allows for extensive use as the material of construction in petroleum industries, chemical processing plants, marine applications, boilers, refinery plants, extractive industries, etc. However, its application under these industrial conditions subjects it to rapid corrosion attack especially in applications involving the extensive use of sulfuric acid and other corrosive media due to their wide range of applications, including domestic acidic drain cleaner, electrolyte in lead-acid batteries and various cleaning agents.1 The most cost-effective and practical corrosion control technique for effectively preventing the occurrence or reducing the severity of corrosion is to alter the electrochemical nature of the environment with chemical compounds known as inhibitors.2,3 Effective corrosion inhibition is subject to the chemical composition, molecular structure and affinity of the inhibiting compound with the metallic alloy surface. Deanol has been used for corrosion prevention in concrete with mixed results. [4][5][6][7] The compound adsorbs through concrete resulting in the formation of a complex precipitate of protective film, which adsorbs onto the metal surface. This provides an impenetrable barrier to metal dissolution that acts to stifle cathodic and or anodic electrochemical corrosion reactions taking place at the metal/solution interface. This investigation aims to evaluate the corrosion inhibition properties of deanol on the electrochemical behaviour of mild steel in aqueous dilute sulphuric acid at ambient temperature of 25 °C.