Abstract
One of the present authors reported a protective method about ten years ago in which specimens of aluminium and duralumin were treated first at 100° with a mixed aqueous solution of CaO, CaSO4 and a small amount of ZnO and then with an aqueous solution of Na2SiO3. In the modified method the specimens were treated at 60° for 2_??_3 minutes with 2% NaOH solution and then with a mixed aqueous solution containing CaO, CaSO4, K2Cr2O7, KNO3, Na2SiO3 and a small amount of KMnO4 for 20_??_30 minutes.
One of the electrolytic process was also attempted in which the, specimens were pretreated for 30 seconis by 2_??_3% NaOH solution at room temperature and then with the electrodes in 25% H2SO4 solution; A. C. being applied for 5_??_60 minutes. The effectivencso of the protective films prepared by means of the above processer against. corrosion by 3% NaCI solution was compared.
