The methods of the rapid detection of aluminium, titanium, and copper which were contained in small amounts in stainless steels were studied with the electrographic technique. Eriochrome Cyanine R for aluminium, Chromotropic acid disodium salt for titanium, and 4-(2-Pyridylazo) -resorcinol (PAR) for copper were employed because of the stability of these complexes in acid and their clear coloration. Barium chloride and EDTA solution were added into acetic acid solution of Eriochrome Cyanine R and hydrochloric acid was added into the Chromotropic acid solution and PAR solution to obtain a high current density and adjust the acidity. Optimum concentrations of the above solutions and conditions of electrolysis for detection of the above elements were given.
The proposed procedure was as follows; The filter paper was soaked in the above solution and then put on the polished surface of the stainless steel sample which was connected with an anode. The electric current was introduced through the filter paper.
The mark of vivid red purple color for aluminium and copper, reddish brown for titanium were directly printed on the filter papers impregnated with above organic reagent solutions.
The limits of detection might be 0.1% for aluminium and titanium and 0.7% for copper.
By this proposed method, reliable and rapid detection of these elements could be done without skilled workers at the factory.