| 摘要 |
550,751. Coating metals. AMERICAN CHEMICAL PAINT CO. April 15, 1941, No. 4930. Convention date, April 13, 1940. [Class 82 (ii)] A continuous process of applying phosphate coatings to iron or steel articles comprises the preparation of a supersaturated cold solution of acid phosphate of manganese, cadmium, calcium, or preferably zinc, adding to such solution a bromate, iodate, picric acid, quinone, or preferably a nitrite, particularly sodium nitrite, the quantity of said compound in the case of sodium nitrite being sufficient to yield a concentration of nitrite of from 12 gm, to 5 gms. per litre or a quantity equivalent in iron dissolving effect in the case of the other compounds, treating the articles in succession with such solution, preferably by spraying, and adding, preferably continuously, such quantities of the phosphate and of the nitrite &c. as to maintain the zinc &c. content and the supersaturation substantially constant. A sufficient quantity of a compound such as sodium carbonate, sodium acetate, zinc acetate, or preferably caustic soda, capable of raising the pH value to such an extent as to cause the solution to be sufficiently supersaturated not to produce the desired coating may be added before the nitrite etc.; or if necessary in some cases the pH value can be lowered to a desired point by additions of phosphoric acid. Grease, dirt &c. may first be removed from the articles preferably by an alkaline solvent. Specifications 386,739 and 501,739 are referred to. |
