pigment molibdico inhibitor corrosion and process for its preparation

摘要

A novel group of corrosion inhibiting pigments has been discovered, which is based on zinc molybdate compounds selected from sodium zinc molybdate, potassium zinc molybdate, ammonium zinc molybdate and mixtures thereof, combined with a suitable carrier, so that the proportion of the zinc molybdate compound is such that the Mo content in the pigment is between about 1 and 30% by weight. Such pigments can be prepared in situ by several methods, such as a double decomposition reaction of sodium, potassium or ammonium molybdate and a solution containing dissolved zinc ion, or an addition of an appropriate acid to zinc oxide dispersed in sodium, potassium or ammonium molybdate solution, or an addition of zinc oxide to a solution which comprises molybdic oxide dissolved in an aqueous solution of sodium, potassium or ammonium molybdate. All these methods are simple, economic and lead to non-toxic pigments of essentially white colour, which have anti-corrosive properties comparable to, or better than, those of zinc yellow and other commercially available corrosion inhibiting pigments.