The search for eco-friendly corrosion inhibitor is essential for the industries where corrosion is a major problem. This book is a report of research jointly carried out by the Femi Awe and Professor Nnabuk Okon Eddy. The research was conducted to investigate the possibility of using some amino acids as inhibitors for the corrosion of mild steel in solutions of HCl. Theoretical (quantum chemical principles) and experimental(gravimetric, gasometric, thermometric and FTIR) approaches were employed in the research. The work is more of a research monograph and were conducted under the supervision and supports of eminent academicians (including Professor U. J. Ibok and Prof. E. C. Gimba). The authors found that amino acids are good corrosion inhibitors and have have also established equations using QSAR that can be used as a guide toward the synthesis of new corrosion inhibitors. Application of condensed Fukui and softness functions as well as relative nucleophilicity/electrophilicity (calculated for B3LYP(6-31G) and MP2(STO-5G) paturbations) yeilded information on the sites for electrophilic and nucleophilic attacks.