Chemical and Electrochemical Studies on Expired Lioresal Drugs as Corrosion Inhibitors for Carbon Steel in Sulfuric Acid

Lioresal is a muscle relaxer and an antispasmodic agent, known as Lioresal. The active ingredient is beta-(Aminomethyl)-p-chlorohydrocinnamic acid, a racemic mixture of the R,(-) and S, (+) isomers. It affects directly the spinal cord with adverse effects including drowsiness, dizziness, weakness, fatigue, headache, trouble sleeping, nausea and vomiting, urinary retention, or constipation. Therefore, the accumulation of expired or unused Lioresal in our home is so dangerous and harmful for our children. The present work introduces an idea for using expired Lioresal as a corrosion inhibitor for steel in 1.0 M H2SO4. The effect of both concentration and temperature were studied. The inhibition efficiency was found to increase with concentration and decreased with rising temperature. Chemical, electrochemical, and analytical techniques, namely, gravimetric, thermometric, gasometric, acidimetric, AAS, and potentiodynamic polarization were used to evaluate the inhibition action of the expired Lioresal drugs. The inhibition performance is due to the adsorption and adhesion of drugs constituent molecules on the steel surface. The adsorption was found to obey Langmuir isotherm. The surface area available for the anodic dissolution of iron and cathodic hydrogen evolution process diminishes without changing the reaction mechanism. The values of Ecorr. readings slowly decrease to negative values, showing that these inhibitors are mixed-type inhibitors mainly cathodic inhibitors. The data obtained from different techniques are in good agreement with each other. Electrochemical and analytical Techniques are efficient and accurate in the determination of the corrosion rate and inhibition performance of expired drugs in an aqueous medium.