Patent GB-390834-A (GB)
Title: Material and method for cleaning and coating metal
IPC: C25D11/24
Filed: 1931-09-24
Abstract: Iron, steel, or zinc surfaces, particularly surfaces which are to be subsequently painted or enamelled, are simultaneously cleaned and coated by treating with a solution which will react with the metal to form a substantially insoluble salt, the solution being applied to the metal in the form of a film, e.g. by spraying or brushing.  A solution described which results in a phosphate coat being formed on the metal comprises fullers earth, cupric nitrate, and a phosphate, e.g. zinc phosphate, manganese phosphate, iron phosphate, or a mixture of manganese and iron phosphates including insoluble ferric phosphate.  The cupric nitrate may be replaced by a soluble copper salt and an oxidizing agent, and in some cases the copper salt may be omitted or replaced by a salt of another metal less basic than iron, e.g. lead or silver.  The solution is dried on the metal, preferably with the aid of heat, and the impurities, grease, rust, &c., which are absorbed by the fullers earth are then brushed off.  The fullers earth may be omitted, particularly in the treatment of zinc or galvanized iron surfaces, the impurities being then washed off when the reaction is complete.  Lactic acid may be added to the solution, if desired, to retard the drying. Solutions containing organic acids, e.g. oxalic, malonic, or tartaric, may be used instead of phosphate solutions, a solution described being substantially saturated with oxalic acid and containing also fullers earth, sodium sulphite, and manganese dioxide.  Alcohol may be added to the solution.  Reference has been directed by the Comptroller to British Specifications 4027/95, 14839/03, [both in Class 82, Metals and alloys], 22743/09, [Class 82 (ii), Washing granular &c.], and U.S.A. Specification 1,290,476.ALSO:Iron, steel or zinc surfaces, particularly surfaces which are to be subsequently painted or enamelled, are simultaneously cleaned and coated by treating with a solution which will react with the metal to form a substantially insoluble salt, the solution being applied to the metal in the form of a film, e.g. by spraying or brushing.  To form a phosphate coat the metal is treated with a solution containing zinc phosphate, iron phosphate or manganese phosphate, and an oxidizing agent.  When manganese phosphate is used it is preferably mixed with some iron phosphate, including some insoluble ferric phosphate.  A soluble compound of copper or other metal less basic than iron. e.g. lead or silver, is preferably added to accelerate the reaction and the copper compound and the oxidizing agent may be added simultaneously, e.g. in the form of cupric nitrate.  The solution preferably contains some inert material such as fuller's earth, which will absorb the grease, rust, &c. removed by the action of the solution and form a loose powdery coating which is burshed off after the solution has been dried on the metal, preferably with the air of heat.  The inert material may be omitted, particularly in the treatment of zinc or galvanized iron surfaces, the dirt &c. being then washed off after the reaction is complete. The acidity and the concentration of the solution should be such that the reaction and the drying of the film are completed simultaneously and a substance such as lactic acid may be added if necessary to retard the drying.  The coating which, when a copper compound is added, consists of phosphates interspersed with metallic copper may be treated to oxidize the copper, for example by raising the temperature during drying, and may then be treated with oil. Coatings may also be formed by treatment with solutions containing organic acids, e.g. oxalic, malonic, or tartaric, a solution described being substantially saturated with oxalic acid and containing fuller's earth as absorbent for grease &c. and sodium sulphite and manganese dioxide as oxidizing and accelerating agents.  Alcohol may be added to the solutions to aid the spreading of the solution over the metal. If the surface to be treated is very rusty more than one treatment with the solution may be necessary.  Reference has been directed by the Comptroller to British Specifications 4027/95, 14839/03, [both in Class 82, Metals and alloys], 22743/09, [Class 82 (ii), Washing granular &c.], and U.S.A. Specification 1,290,476.