PATENT BRIEFS: for the corrosion engineer Available to Purchase

Protection from Brine Solution. Metal and metal alloys can be successfully protected against the corrosive action of calcium chloride and sodium chloride solutions by adding a zinc salt and an alkali metal silicate to the solutions. Protection is afforded at a concentration of 1 to 4 g/l silicate and 0.4 g/l zinc salt. Admixture of silicate with zinc chloride enables a higher inhibiting power to be achieved with less than 2 g/l of silicate. Adding alkali metal chromate as well as silicate and zinc salt improves still further the degree of protection afforded to the metal. Local corrosion can occur where the amount of chromate employed is insufficient. A minimum of 5 g Na2CrO4 per m2 is essential, but for dilute solution an alkali metal silicate/zinc salt treatment keeps the metal very clean. As regards uses to which the discovery can be put, the following are typical of those suggested: refrigeration, drying gases, melting ice and snow and, where calcium chloride is used, for soil stabilisation. (Brit. Pat. 903,937, Solvay et Cie., Belgium.)