Water-conditioning compsn - contg 1-hydroxy-1,1-diphosphonic acid and polyphosphate to prevent metal corrosion and boiler scale

摘要

Circulating water (esp. water cooling systems, heat exchangers and evaporators) is conditioned for lowering corrosive attacks and boiler scale on metal surfaces by incorporating a mixt. contg. 0.5-50 (2-10) p.p.m. of a 1-hydroxyalkylidene-1,1-diphosphonic acid of formula (MO)2-PO-CR(OH)-PO(OM)2 (where R is 1-5C alkyl and M is H, a metal cation, NH4+ or an ethanolammonium ion) in addn. to 1-200 (10-60) p.p.m. of a water-soluble polyphosphate (calc. as PO4) consisting of (1) an inorganic polyphosphate with an 0.4:1 to 2:1 mol. ratio of s=1 alkali-, alkaline earth metal- and/or Zn oxide to P2O5 and/or its corresp. acid with a 0.4:1 to 2:1 water:P2O5 mol. ratio, or (2) a polyfunctional acid phosphate ester of a polyhydric alcohol having formula R-(OPO3H2)x (where R is the hydrocarbyl gp. of a polyhydric alcohol and x is 2 to 6).