| 摘要 |
1,146,358. Preventing corrosion; phosphate solutions. CELANESE CORP. Aug.19, 1966 [Aug.25, 1965], No.37181/66. Headings C7E and C7U. Corrosion of metal equipment, e.g. stainless steel or aluminium tubing in distillation towers and evaporators, in contact with aqueous formaldehyde solution is reduced by maintaining in the solution phosphate ions in a concentration of 10 to 1000 p.p.m. (calculated as H 3 PO 4 ). H 3 PO 4 , alkali metal phosphates e. g. Na 3 PO 4 or Na 2 HPO 4 , amine phosphates including quaternary methyl amine salts or other organic phosphates may be used to yield phosphate ions. Up to 5000 p. p. m. of halogen as halogen-containing contaminants, e.g. methylene or ethylene chloride or bromide or alkali metal halides, may be present in the solution. Formic acid may also be present with the formaldehyde. |
