With the versatility of structural performance in magnesium alloys, Achilles hill remains to be their susceptibility to corrosion. The Mg community agrees that traditional methods are insufficient for revealing the root cause of difficulties in controlling Mg degradation rate. Therefore, developing new methods allowing simultaneous assessment of several characteristics is of great importance now. We designed an advanced cell for immersion testing allowing simultaneous assessment of two complementary characteristics of Mg corrosion in aqueous environments: isothermal calorimetry and pressure. Isothermal calorimetry monitors in situ heat production rate during chemical reactions, which can be recalculated to corrosion rate if the enthalpy of a process is known. Pressure monitoring allows alternative quantification of corrosion rate through hydrogen production. The proof-of-concept testing presented here reveals details of a corrosion process depending on electrolyte.