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Unlted States Patent [19] [11] Patent Number: 4,539,051 Hacias [45] Date of Patent: Sep

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Unlted States Patent [19] [11] Patent Number: 4,539,051 Hacias [45] Date of Patent: Sep Unlted States Patent [19] [11] Patent Number: 4,539,051 Hacias [45] Date of Patent: Sep. 3, 1985 [S4] PROCESS FOR PRODUCING PHOSPHATE 4,497,666 2/1985 Schapira et al. ............. .. 148/615 R COATINGS Primary Examiner~Thurman K. Page [75] Inventor: Kenneth J. Hacias, Sterling Heights, Attorney, Agent, 01‘ Fl'rm—Arthur E. Kluegel . M‘Ch- [57] ABSTRACT [73] Asslgnee: Parker Chewical Company’ Madlson An improved process for activating metal surfaces prior Helghts’ Mlch‘ to a phosphating treatment whereby relatively thin, [21] Appl. No.: 690,431 dense, ?ne-sized and uniform crystalline adherent phos [22] Filed: Jan. 10, 1985 phate coatings are produced providing superior corro slon protection and paint adherence when coated sub Related Us. Application Data strates are subjected to cyclical temperature and ‘ambi ent environments typifying normal service conditions. [63] Continuation-impart of Ser. No. 469,621, Mar. 2, 1983, To prepare the aqueous activating Solution, a dry acti abandoned" vating composition is prepared which is adapted to be [51] Int. Cl.3 ....................... .. C23C 1/10; CZSD 13/00 dispersed in Water at a controlled concentration and [52] US. Cl. ........................ .. 148/615 Z; 148/615 R; which comprises a mixture of about 60 to about 90% by 204/1813; 427/4195; 427/4197 weight of a particulated dried reaction product of a [58] Field of Search ................... .. 148/615 Z, 6.15 R; titanium-containing compound and sodium phosphate 204/181 R, 131 C, 469, 621; 427/409, 419-5, compound containing at least about 0.005% by weight 419-7 titanium with the balance comprising tetrasodium pyro [56] References Cited phosphate. The dry activating composition is dispersed in the aqueous solution to provide a total concentration U.S. PATENT DOCUMENTS of from about 0.1 to about 10 g/l. In accordance with 2,310,239 2/1943 Jernstedt ............................... .. 148/6 the process aspects of the present invention, the aqueous 2,874,081 2/1959 Cavanagh et a1. 148/6115 dispersion containing the activating composition is ap 3,222,226 12/1965 Maurer et a]. .. 148/616 plied to cleaned metal surfaces such as steel, zinc and 3,279,958 l0/l966 Maurer et al. .. 148/616 aluminum before the following zinc phosphating step 3,664,887 5/1972 Atkiss . .. 148/616 4,110,129 8/1978 Matsushima et a1. 148/615 R whereby improved phosphating coatings are produced. 4,152,170 5/1979 Guhde ................... .. 148/615 R 4,165,242 8/1979 Kelly et a1. .................. .. 148/615 Z 27 Claims, N0 Drawings 4,539,051 1 2 tration for activating metal surfaces for subsequent re PROCESS FOR PRODUCING PHOSPHATE action with a high-zinc phosphate coating solution to COATINGS achieve a dense, relatively thin adherent phosphate coating of relatively ?ne-sized crystals generally of a REFERENCE TO RELATED APPLICATIONS 5 size of about 5 to about 10 microns. The dry activating This application is a continuation-in-part of prior composition comprises a particulated mixture contain copending US. patent application Ser. No. 469,621 ?led ing from about 60% to about 90% by weight ofa dried Mar. 2, 1983 now abandoned. reaction product of a titanium-containing compound and sodium phosphate compound containing at least BACKGROUND OF THE INVENTION about 0.005% by weight titanium up to about 5% by A variety of compositions and processes have hereto weight titanium in combination with tetrasodium pyro fore been used or proposed for use for effecting the phosphate. The dry activating composition may option formation of an adherent, uniform phosphate coating on ally, but preferably, further contain up to about 5% by metal surfaces to enhance the adhesion of subsequently weight of monosodium phosphate based on the total applied siccative coatings and to provide for substan 5 weight of the mixture. tially improved corrosion resistance of the coated sub An aqueous bath suitable for activating metal surfaces strate. Phosphate coating processes of the various types prior to zinc phosphating is comprised by dispersing the well known and practiced in the art conventionally dry activating composition in water to provide a con comprise aqueous acidic solutions which are applied to centration of the activating composition within a range a cleaned metal surface such as by spraying, immersion, of about 0.1 up to about 10 grams (g/l) with concentra ?ooding or the like for a period of time suf?cient to tions of from about 0.75 to about 3 g/l being preferred. form a crystalline phosphate coating thereon. Numer The speci?c concentration of the activating composi ous improvements in such phosphate coating processes tion will depend to some extent on the concentration of and compositions have been made since their early titanium present in the reaction product of the activat introduction including the development of an activating 25 ing mixture and is usually controlled within the forego pretreatment to accelerate the formation of a phosphate ing ranges to provide a concentration of titanium in the coating on a metal surface and to increase the unifor activating solution within a range of about 0.001 to mity of the coating produced. One such activating treat about 0.01 g/l. ment is taught in US. Pat. No. 2,310,239 to Jernstedt in which the cleaned metal surface is ?rst contacted with In accordance with the process aspects of the present an aqueous dispersion of a dried disodium phosphate invention, a cleaned, metal substrate is contacted with titanium compound reaction product containing from the aqueous activating solution at a temperature of from about 0.005 to about 20 percent by weight titanium about 75° F. up to about 130° F. for a period of from prior to contact with the subsequent phosphating solu about 15 seconds up to about 5 minutes whereafter the tion. An improved method for producing the phos activated metal surface is contacted with a high-zinc phate-titanium reaction product is taught in US. Pat. phosphate solution of any of the types wellknown in the No. 2,874,081 to Cavanagh and Maurer the teachings of art for forming an adherent extremely ?ne crystalline which are incorporated herein by reference. size dense phosphate coating thereover. Convention The continuing demand for still further improve ally, the phosphated substrate is usually water rinsed ments in the corrosion resistance of metal substrates, followed by a sealing or post treatment rinse which may particularly ferrous-base, zinc-base and aluminum-base contain hexavalent and/or trivalent chromium ions or substrates as employed in automotive applications has may comprise a chromium-free rinse solution to en provided impetus in the development of still further hance the corrosion resistance of the phosphated sur improvements to substantially enhance corrosion pro face. The post treatment rinsed surface is usually sub tection and adherence of various siccative organic ?n 45 jected to a further water rinse and may be subjected to ishes including electrophoretic coatings applied to auto a drying step before one or a plurality of organic sicca mobile body and chassis components. The advent of tive coating are applied thereover. In those instances in more stringent corrosion test procedures adopted by which water base coatings are to be employed such as automobile manufacturers including a so-called cycle cathodically applied electrophoretic coatings, the dry test as an indication of the projected service life of a ing step can be omitted. treated automotive component has rendered many of Additional bene?ts and advantages of the present the prior art phosphating processes and compositions invention will become apparent upon a reading of the de?cient in passing such rigorous test conditions. Description of the Preferred Embodiments taken in The present invention provides for an improved acti conjunction with the speci?c examples provided. vation composition and process for activating metal 55 surfaces prior to a phosphating treatment employing DESCRIPTION OF THE PREFERRED comparatively low concentrations of the activating EMBODIMENTS constituents thereby achieving substantial economy in The dry activating composition of the present inven the treatment of metal surfaces while at the same time tion adapted for‘ dispersion in water for contacting producing comparatively thin, dense, ?ne-size crystal 60 metal surfaces to effect an activation thereof for subse line adherent phosphate coatings providing superior quent reaction with zinc phosphate coating solutions corrosion protection in comparison to prior art compo comprises a controlled mixture of a particulated dry sitions and processes heretofore known. reaction product of a titanium-containing compound and sodium phosphate compound which contains about SUMMARY OF THE INVENTION 65 0.005% up to about 5% titanium in combination with The bene?ts and advantages of the present invention particulated tetrasodium pyrophosphate. It will be un are achieved by providing a dry activating composition derstood that the term “reaction product” as herein adapted for dispersion in water in a controlled concen disclosed and as set forth in the subjoined claims encom 4,539,051 3 4 passes a reaction product produced by forming an aque stantially uniform mixture of these constituents. It is ous alkaline dispersion and/or solution of a sodium further contemplated that monosodium phosphate in a phosphate compound and a titanium compound suffi particulated form can be incorporated in the mixture in cient to provide titanium ions which are reacted for a an amount up to about 5% by weight of the total mix period of time whereafter the aqueous reaction medium ture. is evaporated to dryness and the dry reaction product is In the preparation of an aqueous solution for activat advantageously comminuted to break up any agglomer ing metal surfaces for subsequent treatment in a zinc ates formed. One method of preparing such a reaction phosphate coating process, the dried mixture is dis product is described in Us.
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