Dezincification
of Brass.-Considerable study has been given to this topic which has importance in chemical operations. Abrams (Trans. Awer. Electrochem. Sot., Igzz, 42, 39) found that the process is not the direct solution of the zinc, but the solution of the whole alloy with the subsequent deposition of the copper, and that there is no dezincification unless a membrane is present to hold the copper-rich solution in contact with the brass.
C. F. Nixon, a senior student in the Chemical Engineering Department of the University of Wisconsin presented at the forty-fifth meeting of the American Electrochemical Society in April, 1923, a paper giving further results in the study of the subject starting with Abrams' view. It was found that the presence of oxygen or highly ionized copper is necessary to initiate solution.
Some copper salts, such as acetate, lactate, bromate and per-chlorate do not promote dezincification.
Brass is not the only alloy susceptible of removal of one constituent.
Copperaluminum (70-30)) manganese-copper (25-75) and cadmiummagnesium (85.7-14.3) were found to be subject to selective erosion. It was found that when the amount of copper is go per cent. or over, dezincification is not likely to occur. Monel metal and German silver are resistant.
Tin in brass slows down the dezincification materially. Antimony has little beneficial effect ; nickel and arsenic brasses appear promising and worthy of further study. H. L.