Magnesium is a promising metal for resorbable cardiovascular implants due to its high biocompatibility, high corrosion tendency, and mechanical properties. However, adapting its corrosion rate to the physiological healing processes is required to ascertain a safe graft function. A protective polymeric layer is supposed to slow down the corrosion rate of magnesium. Additionally, coatings can improve the host’s tissue interaction with the implant by implementing the local delivery of antibiotic drugs and growth or cell adhesion factors. However, little is known about the interaction of polymer-based coatings, their degradation, and magnesium corrosion. This study examines the corrosion mechanism of magnesium protected by spin coatings and electrospun fiber coatings under physiological conditions. Pure magnesium specimens were coated with polycaprolactone (PCL). The corrosion of the coated magnesium was evaluated using an immersion test in simulated body fluid. Spin coatings provided efficient protection against corrosive attacks and a significantly lower corrosion rate by 75% compared to uncoated magnesium. In contrast, fiber coatings did not provide relevant corrosion protection. On the other hand, magnesium corrosion caused the accelerated degradation of the PCL layer. A reliable and safe implant function is vital, especially in cardiovascular applications. Magnesium coating, therefore, should be carried out with spin coatings.