1989 Volume 75 Issue 4 Pages 689-695
Colouring solution (composed with CrO3 : 250g/l and H2SO4 : 500g/l) used to colouring method for stainless steels that was developed at Birmingham research institute of International Nickel Corp. is deteriorated according to increase of amounts of colouring treatments.
Deteriorated colouring solution caused troubles of elongation of colouring time e.g. falldown of production efficiency and missing clarity of coloured films So, deterioration behavior and restoration method of colouring ability of the colouring solution were studied. The results are as follows;
(1) Deterioration was caused by comsuptions of chromic and sulfuric acid that were main components of the colouring solution.
(2) And more than 12 g/l of chromium (III) ion, the colouring solution deteriorated the colouring times delayed.
(3) Colouring times turned back to the former level when amounts of comsumed chromic and sulfuric acids were added into the deteriorated colouring solution.
(4) But the colouring times were not recovered for the solutions contained with more than 12 g/l chromium (III) ions even if chromic and sulfuric acids were added.
