Glycol antifreeze - corrosion & scale inhibitors

Antifreezes have been proposed with consist of water-soluble alcohols as the chief nonaqueous ingredients plus anticorrosion agents containing 0.4 to 80% benzotriazole, its ammonium salt, or tetrabortate, or their mixtures. The amount of the agent in the antifreeze is sufficient to produce a concentration of about 0.01 to 2.0% benzotriazole or its salt and 0.5 to 3.0% of the weight of the water soluble alcohols.

Another antifreeze consists of a water-soluble alcohol, particularly ethylene glycol, and an agent containing 0.2 to 77% benzotriazole, its alkali metal or ammonium salt or their mixtures, or N-alkylbenzotriazole; 2.2 to 80% of an alkali metal arsenite, arsenate or molybdate or their mixtures; and 11 to 96% of a material which maintains the pH of the aqueous solution of the anticorrosion agent at about 7.5 to 10.5.  The anticorrosion agent is present in an amount sufficient to produce concentrations of 0.01 to 2.0% benzotriazole; 0.1 to 2.0% arsenite, arsenate, or molybdate; and 0.5 to 2.5% of the buffer.

Other corrosion inhibitors for ethylene glycol solutions have been proposed. For example, one contains 1 part phosphoric acid (density 1.75) and sufficient technical triethanolamine (usually about 3 parts by wt) added to 100 parts ethylene glycol to bring the pH of a 50% aqueous solution of the mixture to 7.2. The resulting composition shows less tendency to corrode metals than a corresponding composition in which the benzotriazole is replaced by 0.2 to 0.3 parts sodium mercaptobenzotriazole.