In this book, the corrosion protection provided by coatings of poly (ether imide)(PEI), poly vinilidene fluoride (PVDF) and polyacrylonitrile (PAN) on magnesium AZ31 alloy sheets in described. The coatings were prepared by spin-coating and dip-coating, using different solutions of the polymers, and the parameters related to the performance of these coatings was investigated by techniques as electrochemical impedance spectroscopy, infrared spectroscopy, x-ray photoelectron spectroscopy and scanning electron microscopy. Special attention was given to interfacial interactions between substrate and polymer as well as interfacial reactions between the coating and the corrosion products. The influence of acid pre-treatments on the coating properties was also investigated. It was observed that a good protection is related to acid-base interactions at the interface and that self-healing process might take place by reactions between polymer the magnesium hydroxide.