International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395 -0056 Volume: 04 Issue: 02 |Feb -2017 www.irjet.net p-ISSN: 2395-0072 © 2017, IRJET | Impact Factor value: 5.181 | ISO 9001:2008 Certified Journal | Page 679 Predictive Model for Corrosion Inhibition of Mild Steel in HCl by Crushed Leaves of Clerodendrum Splendens Agha Inya Ndukwe 1 and C. N. Anyakwo 2 1. Department of Metallurgical Engineering Technology, Akanu Ibiam Federal Polytechnic Unwana, P.M.B. 1007, Afikpo, Nigeria. 2. Department of Materials and Metallurgical Engineering, Federal University of Technology, P.M.B. 1526, Owerri, Nigeria. ---------------------------------------------------------------------***--------------------------------------------------------------------- Abstract - The corrosion inhibition of mild steel in 0.7M, 1.2M and 2.2M HCl by thoroughly crushed leaves of Clerodendrum Splendens has been studied using the weight- loss technique. The corrosion rate curves were observed to continuously decrease with time whilst the inhibition efficiency improved as the experimentation progressed. For the entire study environment, the highest inhibition efficiency of 70.70% was achieved when the thoroughly crushed leaves of Clerodendrum Splendens were added at 45g per litre of 1.2M HCl while the corrosion rate reduced from 0.6738mgcm -2 h -1 to 0.2465mgcm -2 h -1 . The predictive corrosion rate model was developed using multiple regression and artificial neural network. The prediction of the experimental corrosion rate by the artificial neural network revealed the importance of independent variables; (time (h), concentration of acid (M) and quantity of crushed leaves (g)) in the prediction of the dependent variable (Corrosion rate, CR (mgcm -2 h -1 ). The addition of the crushed leaves of Clerodendrum Splendens to the hydrochloric acid induced corrosion of mild steel indicates that the time of exposure vastly influenced the prediction of the corrosion rate by 47.7%, followed by the quantity of pounded leaves, 26.6% and finally the concentration of acid, 25.7%. Predictions by the artificial neural network gave a minimal error and were closer to the experimental corrosion rate values in comparison with the predictions by multiple regression. The protective film formed on the mild steel surface was analyzed by FTIR spectroscopy and Scanning electron microscopy (SEM). The FTIR analysis indicates that the adsorbed constituents of the crushed fresh leaves of Clerodendrum Splendens on the surface of mild steel, immersed at 30g per litre of 0.7M HCl for eight hours is associated with the stretching vibrations of O–H, C≡C and C=C bonds. The SEM image shows that corrosion was localized on the surface of mild steel when immersed in the uninhibited solution of 0.7M HCl but the addition of Clerodendrum Splenden’s pounded fresh leaves at 30g per litre of 0.7M clearly inhibited the mild steel from corrosion. The phytochemical analysis of the leaves of Clerodendrum Splendens reveals the presence of alkanoid, tannin, saponin, phytate, flavonoid and phenol. Key Words: Inhibition efficiency, Hydrochloric acid, Corrosion rate, Clerodendrum Splendens, Artificial eural network, Multiple regression. 1. INTRODUCTION Corrosion is the destructive attack of a metal by chemical or electrochemical reaction with its environment [1]. When a metal interacts with the environment, the tendency of the metal to revert to its original state where it was in combination with other elements is imminent. The overall outcome of corrosion as acknowledged by [2] is that a metal undergoes an electrochemical reaction as a result of its surrounding to form a compound similar to the one from which it was won. The destructive effect of a metal has huge financial toll running into billions. For instance, the total annual corrosion cost in the US rose from $276 billion in 1998 to above $1 trillion in the middle of 2013 and is now estimated at $1.1 trillion for 2016 [3]. The addition of an inhibitor is one of the techniques used to prevent corrosion. Inhibitors are substances that prevent the corrosion of metals and alloys when added in minute quantity to the corrodent. This may be achieved by lowering anodic or cathodic reaction rates or both simultaneously [2]. One of such substances often used as an inhibitor is chromate which is toxic and carcinogenic [1]. The toxicity effect of the known synthesized inhibitors has driven contemporary studies towards the use of plant extracts as anti-corrosion agents, because they are mostly harmless. Green inhibitors like natural products from plant extracts and substances from other renewable sources are of the interest of researchers who are desirous of green chemistry or eco-friendly technologies [4]. This research examines the leaves of Clerodendrum Splendens as a veritable candidate for the inhibition of mild steel in hydrochloric acid. Clerodendrum Splendens (Verbenaceae) is a woody or semi-woody evergreen vine or running shrub to 12ft (3.7m) long that climbs by twining. The leaves are oval to 7in (18cm) long and arranged in opposite pairs [5]. Inhibitors have always been considered to be the first line of defence against corrosion in various industries. A great number of scientific studies have been devoted to the subject of corrosion inhibitors but