Inhibition of Mild Steel Corrosion in Hydrochloric Acid Solution by Ciprofloxacin Drug

The inhibition of mild steel corrosion in hydrochloric acid solution by ciprofloxacin drug as an eco-friendly and commercially available inhibitor was studied at room temperature by weight loss technique. It was found that the test drug has a promising inhibitory action against corrosion of mild steel in the medium investigated. The inhibition efficiency was found to increase with a corresponding increase in the concentration of the inhibitor. It was also found that the adsorption as well as the inhibition process followed a first-order kinetics and obeyed Langmuir’s adsorption isotherm. 1. Introduction Mild steel is extensively used in industries and as a result corrodes when exposed to various industrial environments and conditions. The application of inhibitors has been said to be amongst the most practicable ways for protection of metals against corrosion, especially in acidic media [1–3]. The inhibitive reactivity of an inhibitor is fundamentally affected by the molecular structure of the inhibiting molecules [4, 5]. Most prominent corrosion inhibitors are organic compounds containing nitrogen, sulphur, oxygen, and phosphorus in their functional groups [6–9]. The mechanism of these compounds has been proposed to be the adsorption, by means of lone pairs of electron, of the organic functional groups on the metal surfaces [10]. Furthermore, a good number of drugs are known to posses most of these qualities, and current research has been geared to identify cheap drugs, which are environmentally safe as corrosion inhibitors [11, 12]. The objective of this present work is to study the inhibition of mild steel corrosion in HCl solution by ciprofloxacin drug by weight loss method. 2. Experimental 2.1. Materials A commercially available grade of mild steel (purity = 98% Fe) identified and obtained locally was employed in this study. The sheets of metal were mechanically press cut into coupons of 3？cm × 3？cm × 0.1？cm dimensions. A small hole of about 5？mm diameter near the upper edge of the coupons was made to help hold them with grass hooks and suspend them into the corrosive medium. The coupons were used without further polishing. However, they were degreased in acetone, washed in doubly distilled water, and stored in moisture-free desiccators before use. The inhibitor used in this study was an antibiotic drug with common name: ciprofloxacin, while its systematic name is 1-cyclopropyl-6-fluoro-4-oxo-7-(piperazin-1-yl)-quinoline-3-carboxylic acid. The molecular formula of the drug is C17H18FN3O3 with molecular mass of 331.346？g/moL. Ciprofloxacin has the