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
  • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
  • C23C18/54—Contact plating, i.e. electroless electrochemical plating

Definitions

• ABSTRACT Disclosed is an improved composition and process for the heavy metal displacement plating of a zinc surface.
• the improved process provides for contacting the zinc surface with a solution containing at least one soluble 2 Claims, No Drawings COMPOSITION AND PROCESS FOR 1 DISPLACEMENT PLATING OF ZINC SURFACES BACKGROUND OF THE INVENTION
• This invention relates to a composition and process for forming a coating on the surface of zinc or alloy thereof by contacting said surface with an acidic solution for displacement plating. It is an object of this invention to render such solutions less sensitive to zinc ion content thereby prolonging their useful life and improving the process efficiency. It is another object of this invention to provide an undercoating for paint having excellent adhesion characteristics.
• a desensitized acidic solution for displacement platingcontaining nickel, iron or cobalt, suitable for forming a coating on the surface of zinc or an alloy thereof may be obtained by adding to the solution one or more soluble compounds of a desensitizing metal selected from antimony, tin, copper, lead, germanium, vanadium, arsenic and tungsten. It has also been found that the displacement solution may be rendered less sensitive to zinc ion content by contacting'the zinc surface with a solution of one of the foregoing metals' simultaneously with or prior to the displacement plating.
• this invention includes an acidic solution for'the displacement plating in which a solution containing ionic nickel, iron, or cobalt, is adjusted to the desired pH by adding inorganic and/or organic acids and including a desensitizing metal compound and, if desired, a complexing agent.
• the desensitizing .metal compound may alternatively be employed in a pre-displacementplating treatment.
• Suitable heavy metal'compounds of nickel, cobalt, and iron include the'inorganic chlorides, sulfates, nitrates and carbonates and organic salts such as the acetates and citrates.
• the compound of heavy metal is contained in an amount more than 0.1 g/l, preferably in the range of from 0.1 to SO'g/l calculated as the metal.
• Suitable desensitizing metal compounds include stannous chloride, tin borofluoride, stannous acetate, cupric chloride, cupric sulfate, copper citrate, lead chloride, lead nitrate, lead acetate, germanium chloride, germanium oxide, ammonium metavanadate, sodium arsenate, sodium hydrogen arsenate, ammonium magnesium arsenate, ammonium tungstate, sodium tungstate, potassium tungstate, potassium antimony tartrate, potassium antimony oxalate, sodium tetrachloro antimonate and antimony chloride.
• Such compounds are added to the pretreating solution or the solution for displacement plating in a total amount ranging from 0.001 to 50 g/l calculated as the metal and desirably between 0.01 and 10 g/l. Since no effect can be achieved in an amount less than 0.001 g/l, and no proportional increase can be expected in the efficiency correspondingly to an amount more than 50 g/l, such amounts are economically disadvantageous.
• the compounds When the compounds are to be added to a pretreating solution, they may conveniently be added to the immediately preceding rinsing step or the pickling step.
• Supplemental additives for the displacement solution include buffering compounds and a complexing agent for the metallic ions present in the solution or formed by the dissolution. These compounds include tartaric, citric, malic, oxalic, succinic acids and the like and the salts thereof.
• the amount to be added cannot be standarized depending on the purpose, but generally they are used in an amount ranging from 0.1 to 50 g/l.
• organic or inorganic acids may be used.
• the inorganic acids include, for example, hydrochloric, sulfuric, hydrofluoric, and fluorosilicic, and the organic acids include citric, acetic, and oxalic. Normally, the acid will be present in an amount ranging from -l to 150 g/l. If the desired pH can be obtained, a
• salt of such inorganic or organic acids may be used.
• salts of a heavy metal such as iron, nickel, or cobalt, may be used.
• the pH of the solution is generally maintained at a value less than 7 and preferably 1 to 4.5.
• the process of this invention comprises contacting the surface of zinc or an alloy thereof at a temperature ranging from room temperature to the boiling point of the solution for a sufficient length of time to obtain the desired coating by means of spraying, immersing or brushing, preferably by immersing or spraying for the case where the coating is to be used as an undercoating for painting.
• the coating treatment of this invention may be best effected by combining it with certain pretreating steps and after treating steps.
• the pretreating steps comprise steps for degreasing etching by an acid .or alkali solution, surface conditioning, and washing with water subsequent to each treating step.
• the degreasing step is employed when articles to be surface treated are processed in the presence of oil.
• the pickling step activates the surface of articles to be treated and strengthens the effect achieved by the main plating treatment.
• As an after treatment it is preferable to rinse the formed coating with a dilute aqueous solution of chromic acid.
• the coating may then be rinsed with water and followed by drying.
• the coating then is ready for applying paints or other overcoatings. Both the pretreatments and after treatments referred to hereinbefore are normally effected for several seconds to 30 seconds.
• the process of this invention is adapted for surfaces of zinc or its alloys including electrogalvanized and 3 hot-dip galvanized steel.
• a desensitizing metal compound By virtue of the treatment with a desensitizing metal compound, it is possible to maintain the initial efficiency for extended periods by inhibiting the deleterious effects normally caused by the increase in the amount of zinc ion dissolved in the plating solution.
• the coating obtained according to this invention has an excellent adhesion with paints as compared with phosphate coatings, complex coatings based on oxides and chromating coatings.
• EXAMPLE 1 to 3 The adhesion of a film on galvanized steel after having been treated with the acidic solution for displacement plating according to this invention was compared with the film obtained from a conventional acidic solution for displacement plating.
• Specimens were samples from non-chromating galvanized steel plate 0.27 X 50 X 100 mm having a zinc content of 183 grams/m The specimens were treated in a weak alkaline degreasing agent (Finecleaner, Type 315 prepared by Nihon Parkerizing Co., Ltd.) in a concentration of 20 g/l at 60C for 10 seconds and any trace of the residual degreasing agent was removed by rinsing with water.
• a weak alkaline degreasing agent Feinecleaner, Type 315 prepared by Nihon Parkerizing Co., Ltd.
• the specimens were pickled in hydrochloric acid at 25C for 5 seconds followed by rinsing with water again.
• the thus treated specimens were then subjected to displacement for plating using the compositions indicated at 60C for 5 seconds.
• the specimens were treated in a dilute chromic acid (Percolene" Type 62 prepared by Nihon Parkerizing Co. Ltd.) in a concentration of 20 g/l, followed by removing excess chromic acid solution by squeezing them between rolls and finally drying by means of hot air at 105C.
• the treatments were all effected by immersion.
• composition of the Displacement Plating Solution The solution was prepared by dissolving nickel carbonate (16- grams), hydrochloric acid (35% 30 grams), hydrofluoric acid (55% 3 grams) and citric acid (5 grams) in city water 1 liter. Since the solution was reused repeatedly after the preparation, the components were constantly replenished in order to maintain the composition constant. Zinc was gradually dissolved into the solution from the surface treated and eventually reached a concentration of about 50 g/l. All of the examples and controls contained 65 g/l chloride, 1.6 g/l fluoride, 5 g/l citric acid and were adjusted to a pH of 2.
• Control specimens were also prepared from the same hot galvanized steel plate, plated with nickel, painted under the same conditions except that the solution contained no zinc ion in Control No. l and no arsenic nor stannous nor germanium ion in Control No. 2 and the adhesion of the coated film was tested. Table I shows also results of these controls.
• the specimens were evaluated according to the percentage of peeled area on the folded surface.
• the testing condition can be modified from the severe to moderate ones by inserting a desired number of plates having the same thickness as that of specimens between the confronted surfaces of folded specimens.
• the test results were designated as l T when one plate thickness was inserted, as 2 T when two plates were inserted and as 0 T when no plate was inserted therebetween. Accordingly, the smaller the number of the inserted plates was, the more severe the test condition becomes.
• Each test was repeated for 5 specimens and the average is reported.
• the surface treated specimens were then coated with a polyester paint to a thickness of 12 microns and baked at 275C for 90 seconds.
• Table 1 also shows the Table 11 shows the results obtained.
• the solution was further added with DETA 2Na.2H O (1.35 g/l) in order to enhance the dissolution thereof.
• Controls were prepared by plating nickel in the similar manner as disclosed in Controls 1 and 2 except that 315 prepared by Nihon Parkerizing Co. Ltd.) in a concentration of g/l at 60C for 3 seconds and any trace of the residual degreasing agent was removed by rinsing with water. Then the specimens were pickled in 5% the coatings were applied under the same conditions as 5 hydrochloric acid at C for 5 seconds, followed by in these examples and tested in the same manner as rinsing with water again. The specimens were then disclosed in Example 1 to 3. Table II shows also these treated with a surface conditioning agent having the results for the controls. following composition at 25C for 5 seconds.
• Example 4 The specimens were except that the coatings were applied under the same then coated with a paint under the completely same conditions as in these examples and tested in the same treating conditions as disclosed in Example 4 to 6. manner as disclosed in Examples 1 to 3.
• Table III shows Table IV shows the results obtained on the adhesion also these results for the controls. test.
• EXAMPLES 10 to 11 EXAMPLE 12 show effects obtained in the cases where the article has been pretreated with a solution containing stannous ion or a tungstate as a surface conditioning agent by spraying immediately before the known conventional plating treatment.
• the stannous ion was added as stannous chloride and the tungsten as sodium tungstate.
• Specimens were sampled from non-chromating galvanized steel plate (0.27 X X 100 mm) having a zinc content of 183 grams/m-.
• the specimens were treated in a weak alkaline degreasing agent (Finecleaner, Type This example shows an embodiment in which specimens were treated with a pickling solution containing 50 ammonium metavanadate prior to the conventional treatment for displacement plating.
• Specimens were sampled from non-chromated zinc hot-dip galvanized steel plate (0.27 X 50 X mm) having a zinc content of 183 grams/m
• the specimens were treated with a weak alkaline degreasing agent (Finecleaner, Type prepared by Nihon Parkerizing Co. Ltd.,) in a concentration of 20 g/l at 60C for 3 seconds and any trace of the residual degreasing agent 7 was removed by rinsing with water. They were then pickled in a pickling solution having the following composition at 25C for 5 seconds, followed by rinsing with water.
• a weak alkaline degreasing agent Feinecleaner, Type prepared by Nihon Parkerizing Co. Ltd.
• EXAMPLE 13 Each test is repeated with 5 specimens and the aver- Panels were treated as in Examples 1-3 using 0.3 g/l age reported of antimony added as potassium antimony tartrate as TABLE the desensitizer. The adhesion was tested for displace- Article prepared Comm treated ment plating solution having zinc ion contents of 0, 25, with Zinc and 50 g/l. For comparison, results were also obtained fi gf s' g g'fiffjff using an antimony-free plating solution.
• EXAMPLE 15 The adhesion of painted film was tested for an article EXAMPLE 14 treated with an acid1c so lut1on for the displacement plating according to this invention as compared with In thls example, the adhslon and that for an article treated with a conventional acidic tance were tested for the painted coating on an article solution f the displacement plating, ft aging f treated with a displacement plating solution formulated both acidic solutions according to this invention as compared with that of Specimens were sampled from the Same hot b the P F coatmg the Same yp of artlcle nized steel plate, plated with iron under the same contfeated Wlth a Convemlonal Zmc base P P S SQIu' ditions as disclosed in Example 13 except that the distlonplacement plating solution was replaced by that having sPec1men5 were Sampled f Same hot galva' the following composition and subjected to the same q Steel P and P wlth
• the specimens were then pickled with 5% hydrochloric acid for 3 Controls were prepared by sampling from the same seconds, followed by rinsing with water.
• the specimens were subsequently treated with a solution containing surface conditioner in a concentration of 3 g/l by spraying at 40C for 3 seconds and then with a zinc base hot galvanized steel plate and plating with iron under the same conditions as disclosed in the Example except that potassium antimonyl tartrate was eliminated from the displacement plating solution.
• Specimens were sampled from the same hot galvanized steel plate, plated with nickel by employing the same displacement plating solution without any antimony compound as disclosed'in Control in Example 13 except that after the pickling and rinsing with water, the surface to be treated was sprayed with an aqueous solution of potassium antimonyl tartrate in a concentration of 22 g/l (8 g/l calculated as antimony) as a surface conditioner at room temperatures for seconds and coated with a paint. The adhesion test was conducted in the same manner as disclosed hereinbefore. Table IX shows the results obtained.
• Controls were prepared by plating with nickel and coated with a paint in the same manner as disclosed in Example 15 except the absence of said surface treatment with the solution containing an antimony compound.
• EXAMPLE 17 In this example, the adhesion of painted film was tested for an article in which an antimony compound 5 was added to the pickling solution in comparison with that for a substrate pretreated with a conventional pickling solution.
• Specimens were sampled from the same hot galvanized steel plate as disclosed hereinbefore, plated with nickel by employing the same displacement plating solution containing no antimony compound as disclosed in Control for Example 13 and coated with a paint in the same manner as disclosed in Example 13 except that the article was sprayed with a pickling solution containing 5 g/l of tartric acid and 3 g/l of potassium antimonyl tartrate beside other ingredients at room temperature for 3 seconds.
• the results obtained are shown in Table X.
• Table X shows also the results of the Control in which the substrate was treated in the same manner as disclosed immediately before except that the pickling solution is replaced by 5% HCL solution.
• a process for providing a paint base coating on a zinc or zinc alloy surface comprising contacting said surface with an aqueous acidic composition suitable for the displacement plating of a zinc or zinc alloy surface, consisting essentially of a. a soluble heavy metal compound selected from the group consisting of nickel, cobalt and iron in an amount of 0.1 50 g/l expressed as the heavy metal; and
• a soluble compound of a desensitizing metal selected from the group consisting of antimony, tin, copper, lead, germanium, vanadium, arsenic and tungsten in an amount of at least 0.001 g/l expressed as the metal.

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• Chemical & Material Sciences (AREA)
• Electrochemistry (AREA)
• General Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Engineering & Computer Science (AREA)
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• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Chemically Coating (AREA)
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• 1973
  • 1973-11-02 DE DE19732354911 patent/DE2354911A1/de active Pending
  • 1973-11-02 US US412120A patent/US3930081A/en not_active Expired - Lifetime
  • 1973-11-05 IT IT30909/73A patent/IT1012088B/it active
  • 1973-11-06 GB GB5139273A patent/GB1434822A/en not_active Expired
  • 1973-11-06 ES ES420291A patent/ES420291A1/es not_active Expired
  • 1973-11-06 FR FR7339405A patent/FR2205580B1/fr not_active Expired

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