This book gathered new information on the corrosion processes as well as the inhibition of mild steel in acid media by four quinoxalines compounds. The corrosion cost exceeds billions of dollars and modern science tends to remedy or limit these huge losses. One way to protect the corrosion is the use of organic inhibitors. The databases provide about 40,000 documents (papers, review, books ...), hence the growing interest in these investigations. We deal in this book, the effect of four types of molecules "quinoxaline" after an overview on the various quinoxalines studied, using several techniques are used as weight loss, polarization curves and spectroscopy Electrochemical impedance. In addition, we call upon the determination of the quantum indexes trying to explain and correlate between inhibtrice found efficiency and molecular structure.