PURPOSE: To produce corrosion resistant coating clad Al articles having high fixability by treating the Al articles with an aq. Cr2O3 K2Cr2O7(NH4)2SiF6 soln. having a specific compsn. and an aq. alkaline soln. contg. SiO2 and Na2O at specific ratios.

CONSTITUTION: After the Al or Al alloy articles are washed with an aq. acidic soln., the Al articles are brought into contact with the aq. soln. of pH of about 0.5 to 1.0 contg. 70 to 80wt.% Cr2O3, 20 to 30% K2Cr2O7, 2 to 4% (NH4)2SiF6 for about 3 minutes and further, the articles are brought into contact with the aq. soln. of pH about 1.2 to 1.9 kept at ordinary temp. The resulted Si- chromate coated articles are rinsed with water of about 43 to 71°C. The articles are thereafter brought into contact with the aq. alkaline soln. contg. SiO2 and Na2O at a weight ratio of SiO2/Na2O; 2.4 to 3.25 and having 40 to 42° Baume at 20°C and pH of about 11 to 12 for about 1/2 to 2 minutes at about ordinary temp. to 54°C. As a result, the Al articles clad with the fixed transparent and thin corrosion resistant coating contg. the chemical complex consisting of about 9.9 to 12.1 Na2O, 4.1 to 4.3% Cr2O3 and 76.8 to 91.2% SiO2 and having the excellent high-temp. corrosion resistance are obtd.