Corrosion of aluminum alloys in mortar containing sodium, calcium and chloride ions have been studied by weight loss and electrochemical measurements. The ions were added into mortar in the amount of 3%CaCl₂ and 3%NaCl. The corrosion product of aluminum alloys in mortar containing 3%CaCl₂ was identified as 3CaO·Al₂O₃·8H₂O by X-ray diffraction. The corrosion was inhibited by precipitation of the corrosion product and the rate of corrosion was almost proportional to the passivation current. When both 3%CaCl₂ and 3%NaCl were added in mortar, the corrosion product was found to be trihydrated aluminum oxide. The corrosion weight loss was approximately 3 times that in mortar containing 3%CaCl₂ and one-fourth that in mortar containing no CaCl₂ nor NaCl. It is concluded that calcium ions inhibit and sodium ions accelerate the corrosion of aluminum alloys in mortar.