| 摘要 |
<p>1397451 Descaling metal surfaces MONSANTO Ltd 11 Sept 1973 [9 Oct 1972] 46402/72 Heading C7E Iron and Cu oxides are removed, e.g. from boiler pipes, using an aq. solution of pH # 7À0 containing an aliphatic phosphonate and an inorganic NH 4 salt. The phosphonate may contain a group where Y and Y' are each H or C 1-4 alkyl, R and R' are each H, an esterifying group or a cation (e.g. alkali metal, NH 4 , Zn or an amine cation) such that the compound is water soluble to pH # 7À0, and the C atom is attached to the N of ammonia or an aliphatic mono- or diamine e.g. ethylene or hexamethylene diamine. Specified phosphonates are ammonium 1-hydroxyethylidene-1,1- disphosphonate and ammonium aminotri (methylene phosphonate). The NH4 salt may be the chloride, bromide, nitrate, sulphate, carbonate, persulphate, sulphamate, nitrite, or a phosphate. Other additives include H 2 O 2 , persulphates, sulphites and hydrazine.</p> |
