SOME RELATIONS OF COMPOSITION TO SOLUBILITY OF ENAMELS IN ACIDES1

Abstract

Review of literature.—The literature on acid resisting enamels and glasses is reviewed. Acid resisting powers produced by different oxides.—When substituted one for another, in each case in equal percentage amounts, various oxides and minerals increased the resistance of various enamels to the action of boiling 20 per cent hydrochloric acid in the following order of effectiveness: Al2O3, cryolite, Na2O, PbO, BaO, Li2O, MgO, CaF2, ZnO, SrO, CaO, B2O3. The first five mentioned were especially effective. The remainder are undesirable materials from the standpoint of acid resistance. Effect of the enamel base.—The relative effects of the materials were the same for various base enamel compositions. Effect of ZrO2 and TiO2.—ZrO2 and TiO2, when substituted for small amounts of SiO2, increased the resistance of various enamels to attack by acids, ZrO2 being most effective in this respect. The favorable action of ZrO2, is offset by a tendency to produce excessive chipping. Rutile gives less chipping than either zirconia or silica and greater acid resistance than silica. Best compositions.—Enamels 2,17,19,26,27, and 33 of table 1 showed resistance to action of the acid equivalent to that of the original competitions based on the analysis of a French acid-resisting enamel. By use of the data developed in this investigation other highly acid-resisting compositions can readily be formulated.