2,38%,4'293 BBUNG MCQUEB, Clifford gay Rollo, Yonkers, N. Y“ assignor to inter-chemical Qorporation, New York, N. ‘1., a corporation of @hio No Drawing. Application Gctober 10, 1940, Serial No. $60,608 3 (Claims. ($1. 117-—46) This invention relates to the coating of radio ‘is to be formed, an upper limit of 11/2 to 1 is tube plates, and to compositions useful in their desirable. A typical example of my invention is ‘the manufacture. ‘ following: In the manufacture of plates for radio tubes, it Parts‘ by is desirable to obtain a black surface which will withstand high temperatures and dissipate heat . weight rapidly. This may be done at considerable ex 1/2 sec. R. S. nitrocellulose (30% alcohol)__ 14.6 pense by the deposition of a black metallic deposit Camphor 13.7 on the formed plates. Attempts have been made Solvent (5 volumes toluene, 2 ethyl acetate, to reduce cost by applying an organic coating 10 2 butyl acetate, 1 butanol) ______'ll 7 containing black pigment to strip metal, drying This lacquer contains 10.2 parts by weight dry the coating, forming the plates from the strip nitrocellulose. It is used with 1/4 pound per gal metal, and then heating the plates to about 900° lon of super-?ne aluminum lining bronze, and C. in an atmosphere of hydrogen to char the coat 15 applied to strip steel. The coating is dried, and ing. While fair results can be obtained by this the desired plates are then formed, and heated in method, using ordinary nitrocellulose lacquers, hydrogen at 900" C. for ?ve minutes. An adher the base metal must be sandblasted before coat ent dull black deposit is formed. ing in order to get proper adherence of the Other plasticizers may be used in addition to charred coating after heating, so that the expense the camphor, provided enough camphor is present of the process is considerably increased. to give the desired blackness of ?lm. I have discovered that successful adhesion to Obviously, examples may be multiplied inde? metal can be obtained in the process described nitely without departing from the scope of my above, together with a black film, by coating the metal before heating with a lacquer the solid invention, which is defined in the claims. . I claim: ‘ content of which is essentially nitrocellulose, at 1. A lacquer comprising aluminum bronze pow least an equal quantity of camphor, and a small der in a vehicle consisting of a solution of nitro proportion of a “bronze” powder (a metallic pow cellulose and camphor in volatile organic sol der, preferably aluminum). ' vents, the camphor being present in at least as The lacquer appears to have adhesion to the great quantity as the nitrocellulose, and not ex metal after charring because of the aluminum ceeding 11/2 times the quantity, the nitrocellulose bronze carried by it. I believe the metal unites and camphor together equalling at least four su?‘iciently with the base metal at 900° F. to give . times the weight of the bronze, the lacquer being adhesion. However, the resultant color is grey, characterized by the fact that it produces ?lms and the addition of black pigment to the lacquer on metal which can be carbonized by heating in spoils the adhesion. The greyness cannot be hydrogen to 900° C., to produce black surfaces overcome by the char produced from ordinary which will withstand high temperatures and dis nitrocellulose lacquers; and I have discovered sipate heat rapidly. that camphor, of the known nitrocellulose plasti 2. The method of ?nishing which comprises cizers, has the unique property of producing with applying to metal the lacquer of claim 1, drying nitrocellulose a charred ?lm of sumcient black the lacquer and heating the ?nished metal in ness to cover the greyness of the aluminum pow hydrogen at about'900° C. to char the lacquer der, provided it is used in at least equal parts ?lm and produce a metal carrying an adherent by weight with the nitrocellulose. . ,About enough bronze powder should be used black deposit. _ to obtain coverage; this will depend on the par 3. A lacquer comprising aluminum bronze pow ticular bronze used. I prefer not to use over about der in a vehicle consisting of a solution of nitro 1/2 pound of bronze per gallon of lacquer, and cellulose and camphor in volatile organic sol vents, the camphor being present in at least as have obtained best results with about 5/4 pound great quantity as the nitrocellulose, the nitro of very good covering bronze. . The weight of nitrocellulose and camphor 50 cellulose and camphor together equalling at least should be at least about 4 times the weight of four times the weight of the bronze, the lacquer bronze used in order to develop the proper black being characterized by the fact that it produces iilms on metal which can be carbonized by heat ness. I prefer to use as large an excess as possi ing in hydrogen to 900° C., to produce black sur ble, so that I prefer low viscosity (5 seconds or faces which will withstand high temperatures and less) nitrocellulose. 55 The proportion of camphor to nitrocellulose dissipate heat rapidly. may be varied from 1 to 1 up to the point where ‘ ‘ CLIFFORD JAY ROI-LE. the lacquer is too soft to handle. Where the ?lm