Chromium, liquid etching

The solutions accumulate gradually dissolved material from the plastics and from time to time have to be discarded and replaced disposal presents environmental difficulties and for this reason efforts have been made to find alkaline rather than acidic liquids which are capable of etching satisfactorily but do not contain chromium. At the time of writing, unfortunately, development has not reached the stage at which the process based on chromic acid can be superseded for the entire range of substrates. 

A sample of 1 to 5 g, kept between chromium or platinum coated tweezers, is dipped for 45 s in a 100 ml etching bath composed of 1 volume of hydrogen peroxide (30 %) and 3 volumes of acetic acid (97 %) at room temperature and rinsed in 200 ml of water at 60-70 C. Both liquids are magnetically stirred. For each sample fresh solutions are used. 

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