GB801759A - Improvements in or relating to heat exchange systems and compositions for cleaning such systems - Google Patents

Abstract

801,759. Removing incrustation. KELLEY, E. J., and SMITH BROS. & CO. (CHEMICALS), Ltd. Dec. 28, 1956 [Jan. 31, 1956], No. 3129/56. Class 123(1) Scale and insoluble corrosion products in a heat exchange system employing an. aqueous medium, such. as the cooling system of an internal combustion engine, are removed by introducing into the medium an aminopolycarboxylic acid, an aminophosphoric acid or an alkali metal or ammonium salt thereof, the substances dissolving the scale &c. during the normal running of the engine, without harmful effect on the cooling system, which can then be drained at a convenient time. The aminopolycarboxylic acids and aminophosphoric acids are the condensation products of acids such as acetic, oxalic, citric and tartaric acids and phosphoric acid respectively with amines such as primary, alkylenediamines suitably containing from two to six carbon atoms and primary arylenediamines, the preferred aminopolycarboxylic acid being ethylenediamine-tetraacetic acid and its preferred alkali metal salt being the sodium salt. The preferred aminophosphoric acid is ethylenediaminephosphoric acid and its preferred alkali metal salt is the sodium salt. The composition may also include one or more alkali metal, ammonium or amine salts of phosphoric, acetic, oxalic, citric or tartaric acids, and an anti oxidant such. as 2:4-dimethyl-6-tert.-butylphenol may also be added. In an example, eight parts of tetrasodium ethylenediamine tetraacetate are dissolved in 12 parts of water, 0.5 parts of ammonia solution (Sp.Gr. .880) are added and finally the solution is adjusted to pH 3 to 7 with orthophosphoric acid to form a solution for cleaning the water cooling system of a road vehicle.