Classifications

• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C22/73—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals characterised by the process
  • C23C22/76—Applying the liquid by spraying

Definitions

• 148-615 Z 6 Claims ABSTRACT OF THE DISCLOSURE There is disclosed a method for applying protective chemical coatings to metal surfaces to improve their paint adhesion properties and/or corrosion resistance by sequentially spraying onto said surfaces, through a nozzle system on a single hand wand, a cleaning solution at high pressure such as 300600 p.s.i., a chemical coating solution at a low pressure such as 80 p.s.i., and a final passivating rinse. Water rinses may also be applied through the same hand wand mounted nozzle system.
• the method is capable of applying zinc phosphate coatings to ferriferous and zinciferous surfaces, as well as other types of chemical coatings to a wide variety of metal surfaces.
• This invention relates to the art of applying chemical coatings to metal surfaces to prepare them for painting or to increase their corrosion resistance. It particularly involves a novel method of applying such coatings.
• the method is capable of use with a wide variety of protective coatings for metals, but it is of particular utility in the field of applying zinc phosphate coatings to ferriferous and zinciferous surfaces. For this reason, the following discussion will be cast principally in the context of zinc phosphate coatings.
• the foregoing sequence of steps is usually performed in a spray tunnel having a number of separate stations for each step in the process.
• the parts to be coated are carried through the spray tunnel on a conveyor and as they pass through each processing station, one step in the process is performed.
• the equipment involved includes not only the spray tunnel and its conveyor equipment, but also a solution tank, spray risers, and pumping equipment for each processing step, including the water rinsing steps.
• the solution tanks for each processing stage are very large, compared to the volume of solution in contact with the metal parts being processed at any given moment, and for reasons of economy, the solution falling out of contact with the parts is recycled into the solution tank even though it is partially chemically depleted.
• one or more of the spray coating stations in a tunnel-type system is replaced by a dip tank large enough to accommodate parts being coated as they move along the conveyor.
• Such systems still involve the use of large volumes of solution and require control measurements and solution replenishment.
• the spray tunnel system for applying protective coatings to metal parts involves a large capital investment, and requires careful operational control. These factors, as a practical matter, limit its use to mass production operations where many parts of moderate size are to be substantially continuously given protective coatings. This has limited the field of use of protective coatings for metals and has effectively denied their advantages to many potential users. For example, very large parts cannot be treated in a tunnel system unless a commensurately large tunnel is provided, one so large that it is economically impractical. It is also impractical to use such a system in the field, such as at a construction site, or at the location of an installed machine which is being repaired and refurbished.
• tunnel technique is difiieult to adapt to production situations where parts of varied size and shape must be processed and the number of any given type part is relatively small. Finally, some plants have a need to operate a metal coating installation only on an intermittent, sporadic basic and cannot justify the large capital investment in tunnel-type equipment.
• the steam application method has severe limitations, however, which have circumscribed its success. For one thing, chromate coatings and zinc phosphate coatings cannot be suitably applied, and the method is therefore effectively limited to the application of iron phosphate to ferriferous surfaces. Since the solutions are applied at very high temperatures, any volatile components are driven from the solution. Thus nitrite ion will be evolved as oxides of nitrogen.
• zinc phosphate coatings which makes them unsuitable for application by the steam process is that such coatings, when fresh, are particularly susceptible to the rapid formation of light rust in a hot humid environment, such a phenomenon being termed rust blushing. When the application of a zinc phosphate coating is attempted by the steam method, it is found that the surfaces rust blush severely.
• a new method of applying protective coating which does not require the large capital investment, and complex op erating procedures of the spray tunnel and dip tank systems, and which overcomes the disadvantages and limitations of the steam application system.
• the method involves the application of cleaning solution, coating solution, final rinsing solution, and any desired Water rinses sequentially through a nozzle system mounted on a single hand wand.
• the method is adaptable to field use, to use with large parts, to short or intermittent production runs, and to coating situations where flexibility in coating time, cleaning time, and the like is required.
• the method can be used with a wide variety of protective coating systems, and in this respect is more flexible than the steam application method, which, as noted, can only be used with iron phosphate coatings.
• the method the invention is capable of applying good quality zinc phosphate coatings to ferriferous and zinciferous surfaces.
• the metal to be coated is first cleaned by a cleaning solution passed through the nozzle of the hand Wand at high pressures in the range of 300-600 p.s.i., preferably near 500 p.s.i. Then the surface may be rinsed, if desired, and coating solution is sprayed onto the surface at a relatively low pressure, preferably about 80 p.s.i., through the same hand wand mounted nozzle system. Following application of the coating chemicals the surface may again be rinsed, if desired, and then a final passivating rinse solution is sprayed onto the surface through the nozzle of the hand wand, at a relatively low pressure, preferably about 80 p.s.i.
• the application pressure for the final passivating rinse is not as critical as that for the application and cleaning steps, but since completely satisfactory results are obtained at low pressures, it is preferred for reasons of convenience to use such low pressures.
• the temperatures of application are also important factors in the method of the invention. It is preferred that the cleaning step be performed at a relatively low temperature between about room temperature and 150 F. both for reasons of economy and to minimize the contribution of the cleaning step to rust blushing when zinc phosphating is being done. It is preferred that the coating materials be applied at relatively low temperature also, for example between 110 F. to 150 F. The use of coating temperatures toward the high end of this range results in more rapid coating formation, although uniform coatings can be obtained throughout the temperature range. If coating temperatures above 150 F. are used in the coating step of the method, the likelihood of rust blushing is increased, as is the likelihood of evolution of volatile components such as the loss of nitrite ion as oxides of nitrogen.
• the temperatures of the passivating rinse step and of water rinses are preferably about 150 F. In field use the method can thus be readily practiced at a single temperature which is suitable for all of the processing steps including the water rinse steps.
• the considerations outlined above are illustrated by the following examples.
• EXAMPLE 1 The effect of the application pressure for the cleaning step of the method is illustrated by the following tests.
• a mild titanated alkaline cleaner was sprayed for 30 seconds onto a series of lightly oiled steel panels at varying pressures for 30 seconds.
• the application temperature was 110 F.
• a conventional zinc phosphate solution was then applied to the panels for one minute at 70 p.s.i., and the coating appearance was rated visually.
• Table 1 reports the results of this series of tests.
• the column headed water break represents an evaluation of the cleanliness of the work as measured by the uniformity with which the water left the surface without beading up.
• Table 2 shows that in the low pressure ranges of about 20 to about p.s.i. good phosphate coatings are produced. It should also be noted that at the application temperature used in this test, no rust blushing was encountered.
• EXAMPLE 3 A further series of tests was made to illustrate the effect of coating solution application temperature upon coating quality.
• the coating application pressure was maintained at 80 p.s.i., while the coating solution temperature was varied.
• a conventional zinc phosphate coating solution was employed, and the coating time was one minute.
• the cleaning step was performer at 500 p.s.i. and at 150 F. The results are reported in Table 3.
• the large solution tanks characteristic of the spray tunnel and dip tank systems are eliminated.
• Cleaning material, coating material, and passivating rinse material are provided in small tanks or drum of concentrated pre-mix solution and are metered into water supplied from the water mains as it is pumped to the nozzle system on the hand wand.
• the pre-mix tanks or drums need not be heated, when the water from the mains is hot or is heated by an auxiliary heater.
• Mixing valves or similar devices associated with the spray Wand feed equipment may be utilized to adjust the proportion of each of the pre-mixes fed to the water from the mains in order to deliver to the nozzle system solutions of the appropriate dilution.
• the method may be used with the various kinds of coating solutions known to the art.
• the proportions of components of any particular type of coating solution at use dilution are preferably approximately the same as those used in spray tunnel systems.
• zinc phosphate coating solutions are used, and when nitrite ion is used as an accelerator, in accordance with the art, care should be taken to maintain the phosphate solution in the pre-mix tank at a sufficiently low concentration that the nitrite ion is not dissipated as evolved nitrogen dioxide gas.
• titanated cleaner such as a mild alkaline cleaner containing col- I loidal titanium salts
• the cleaner pre-mix solution should be stirred to maintain the colloidal salt in good suspension.
• Treating times for each of the steps of the method may be varied over a considerable range, in accordance with the judgment of the operator as he observes the results of his work.
• adequate final coatings can be obtained by contacting each section of the surface to be coated with cleaning solution for about 30 seconds, with the coating solution for about 30 seconds, and with the final rinse for about 30 seconds.
• the water rinses, if employed, may be applied for about 30 seconds.
• the method of the invention involves the sequential spraying of solutions through the Wand at widely differing pressures, it may be desirable to employ a nozzle having alternately useable orifices of different sizes, or to employ a multiplicity of nozzles on the wand which are alternately operated.
• nozzle and nozzle system are employed herein in a broad sense to connote not only a single nozzle, but also such specially refined nozzle systems.
• a method for applying a protective chemical coating to a metal surface comprising sequentially delivering to said surface through a nozzle mounted on a hand held wand a cleaning solution at a pressure between about 300 p.s.i. and about 600 p.s.i. and a temperature between about 70 F. and about 150 F., a chemical coating solution at a pressure between about 20 p.s.i. and about 80 p.s.i. and a temperature between about 110 F. and about 150 F., and a final passivating rinse solution.
• a method in accordance with claim 1 in which a portion of the aqueous component of each of said solutions is supplied from a main, in which the remaining components and the remainder of the aqueous component are supplied as concentrated premixes, and in which each of said solutions is formed by admixture of its premix and said aqueous component portion in the course of delivery thereof to said hand wand mounted nozzle.
• a method for applying a zinc phosphate coating to ferriferous and zinciferous surfaces comprising sequentially deliverying to the surface to be coated through a nozzle mounted on a hand held wand an alkaline cleaning solution at a pressure between about 300 p.s.i. and about 600 psi. and a temperature between about F. and about 150 F., a zinc phosphate coating solution at a pressure between about 20 psi. and about psi. and a temperature between about F. and about F., and a final passivating rinse solution.

Landscapes

• Chemical & Material Sciences (AREA)
• General Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Chemical Treatment Of Metals (AREA)
• Application Of Or Painting With Fluid Materials (AREA)
• Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=21903982

Family Applications (1)

Country Status (9)

Cited By (3)

• 1970
  • 1970-05-20 US US39160A patent/US3684588A/en not_active Expired - Lifetime
  • 1970-10-01 CA CA094,585A patent/CA947187A/en not_active Expired
• 1971
  • 1971-03-29 BR BR1902/71A patent/BR7101902D0/pt unknown
  • 1971-05-19 GB GB05740/71A patent/GB1298173A/en not_active Expired
  • 1971-05-19 SE SE06546/71A patent/SE368964B/xx unknown
  • 1971-05-19 NL NL7106941A patent/NL7106941A/xx unknown
  • 1971-05-21 FR FR7118482A patent/FR2093597A5/fr not_active Expired
  • 1971-05-21 DE DE19712125328 patent/DE2125328A1/de active Pending
  • 1971-05-21 ES ES391652A patent/ES391652A1/es not_active Expired

Also Published As

Similar Documents

Legal Events