US3171766A - Bright polishing of cadmium and zinc - Google Patents

Bright polishing of cadmium and zinc Download PDF

Info

Publication number
US3171766A
US3171766A US228252A US22825262A US3171766A US 3171766 A US3171766 A US 3171766A US 228252 A US228252 A US 228252A US 22825262 A US22825262 A US 22825262A US 3171766 A US3171766 A US 3171766A
Authority
US
United States
Prior art keywords
ion
zinc
bath
molybdate
per liter
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US228252A
Inventor
Kenneth P Bellinger
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Conversion Chemical Corp
Original Assignee
Conversion Chemical Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Conversion Chemical Corp filed Critical Conversion Chemical Corp
Priority to US228252A priority Critical patent/US3171766A/en
Application granted granted Critical
Publication of US3171766A publication Critical patent/US3171766A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

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
    • C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
    • C23F3/00—Brightening metals by chemical means
    • C23F3/04—Heavy metals
    • C23F3/06—Heavy metals with acidic solutions
    • 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
    • C23C22/05—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 using aqueous solutions
    • C23C22/06—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 using aqueous solutions using aqueous acidic solutions with pH less than 6
    • C23C22/40—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 using aqueous solutions using aqueous acidic solutions with pH less than 6 containing molybdates, tungstates or vanadates
    • 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
    • C23C22/05—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 using aqueous solutions
    • C23C22/06—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 using aqueous solutions using aqueous acidic solutions with pH less than 6
    • C23C22/40—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 using aqueous solutions using aqueous acidic solutions with pH less than 6 containing molybdates, tungstates or vanadates
    • C23C22/44—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 using aqueous solutions using aqueous acidic solutions with pH less than 6 containing molybdates, tungstates or vanadates containing also fluorides or complex fluorides

Definitions

  • zinc surfaces refers to surfaces of zinc and zinc-base alloy articles and other metallic articles having a coating of zinc or zinc-base alloy such as produced by hot-dipping or electroplating.
  • cadmium surfaces refers to surfaces of cadmium and cadmium-base alloy articles and other metallic articles having a coating of cadmium or cadmium-base alloy such as produced by electroplating.
  • Another aim is to provide a simple and effective dilute single-dip composition and method for treating surfaces of zinc and zinc-base alloys to impart a bright finish thereto.
  • a further aim is to provide a self-contained dry powder composition for addition to water which will yield a bath for finishing zinc surfaces and cadmium surfaces to impart protection thereto.
  • the dilute baths of the present invention contain essentially about 0.2-6.5 grams per liter molybdate ion, 4.0-1000 grams per liter of nitrate ion, ⁇ Ll-15.0 grams per liter of activating ion selected from the group consisting of fluoride and sulfate, and up to about 4.0 grams per liter of a leveling ion selected from the group consisting of borate and acetate.
  • the nitrate ion should be maintained at a weight ratio relative to the molybdate ion in excess of about 10:1 to obtain desirable brightening but less than about 40:1 for desirable corrosion protection, and preferably on the order of 30:1.
  • Leveling agents are desirably incorporated in the bath for pH control and control of the rate of bath action to achieve optimum brightening without the need for as critical control of times and temperatures. As little as 0.05 gram per liter will produce a beneficial effect, and amounts up to about one-third the weight of molybdate and activating ion, or about 4.0 grams per liter may be utilized, although the corrosion protection will generally be reduced by increasing concentration of the leveling ion. Accordingly, it is preferred to use only about 0.1-0.8 gram per liter for optimum brightening and corrosion protection. Borates and acetates have proven satisfactory as leveling agents.
  • the baths of the present invention have proven highly effective in providing both brightness and corrosion protection upon Zinc surfaces, the brighter finishes surprisingly demonstrating good corrosion protection, and the dull finishes generally exhibiting considerably lesser or no significant degree of corrosion protection as measured by the lead acetate test. 1
  • the present invention may be utilized to produce a bright finish upon cadmium surfaces under closely controlled conditions, generally there is produced a finish which varies from a cloudy film or yellow or blue iridescent to dull grey in appearance but which does provide some measure of corrosion protection. Accordingly, the present invention in its preferred aspect is directed to the treatment of zinc surfaces.
  • the several ions can be added to the bath as the acid or as salts which are soluble in water or acid solutions.
  • the alkali metal molybdates and particularly sodium molybdate have been advantageously employed.
  • finishing baths in accordance with the present invention and utilizing nitric acid are as follows:
  • SULFATE ION Range Optimum Alkali Metal illolybdate 0 5-8.0 g 2.0 g. Alkali Metal Bisulfate 0.5-8.0 2.0 g. Boric Acid Up to 5.0 g 0.15 g. Nitric Acid, 42 Baum (ill-100.0 ce 24.0 cc. Water To 1.0 liter To 1.0 liter.
  • a self-contained dry powder formulation can be prepared which will form the desired bath upon addition to water.
  • Alkali metal-hydrogen and ammonium-hydrogen salts of fluoride and sulfate have been particularly useful as has urea nitrate for this purpose.
  • a dry powder formulation for addition to water contains essentially about 2.0-8.0 percent by weight alkali metal molybdate; 10-400 percent by weight of an A drop of an aqueous solution containing 5 percent by weight lead acetate is placed upon the surface and the time noted util the spot turns black. Generally 10 seconds is 111- dicative of a high measure of protection since an untreated panel will turn black immediately.
  • activatin a cut havin an anion selected from the roup D b O 1 consisting of sulfates and fluorides and a positive radical selected from the group consisting of alkali metal-hydrogen, alkali metal and ammonium-hydrogen; up to 8.0 percent by weight of a solid leveling agent having an anion selected from the group consisting of acetate and borate and a cation selected from the group consisting of hydrogen, alkali metal and ammonium; and '50.095.0 percent by weight of a nitrate compound having a cation selected from the groupconsistin'g of alkali metal, urea and amrnonium, at least one of said components being sufficiently acidic in nature to provide a pH of 0.52.2 upon addition of the composition to water in sufficient quantity to provide about 0.258.0 grams per liter of alkali metal molybdate.
  • FLUO RIDE ION Either'type of dry powder formulation may be added .to water in amounts sulficient to provide the desired concentration of molybdate ion; i.e., about 0.26.5 grams per liter or about 025-80 grams per liter of alkali metal molybdate. Generally, this will require about 100-1000 grams of powder formulation per liter of water. 'T he pH of the resultant bath will vary with the concentration of the acidic component within the powder formulation and within the bath.
  • the baths of the present invention are employed at ambient temperatures of about 6590 degrees Fahrenheit and require immersion for short periods of about five to thirty seconds, preferably with mild agitation. However, low elevated temperatures of up to about 120 degrees Fahrenheit may be used, although with lesser control and shorter dip times. The workpieces are then rinsed in cold water.
  • tion such as rigid polyvinyl chloride or glass fiber reinforced resin.
  • Exemplary of the efiicacy of the present invention are the following specific examples wherein test panels 2 inches x 3 inches were electroplated with zinc or cadmium and immersed in the several formulations under equivalent conditions of temperature, time and agitation.
  • Example 1 A bath was prepared by admixing 2.0 grams sodium acid fluoride, 1.35 grams sodium molybdate, 0.14 gram boric acid and 21.0 cc. of 42 Baum nitric acid in water to make 1.0 liter. The pH of the bath was measured at 1.35 using a reference solution of pH 1.1.
  • a steel test panel 2 inches x 3 inches having an electro plated zinc coating thereon was immersed in the bath at room temperature for about twelve seconds with agitation and then rinsed in cold water.
  • the resultant finish was bright and free from iridescence.
  • a drop of 5.0 percent by weight lead acetate solution did not turn the finish blacr for over twenty seconds, indicating a high degree of corrosion protection.
  • Example 2 Example '3 A bath was prepared by dissolving in one liter of water 2.0 grams of sodium-hydrogen fluoride, 1.35 grams of sodium molybdate, and 30.0 grams of urea nitrate. The resultant pH was 1.8.
  • a zinc-plated steel test panel Zinches x 3 inches was immersed therein at room temperature for about twelve seconds and then rinsed. The resultant finish was bright and gave a value of twenty seconds in the lead acetate test, indicating a high degree of corrosion protection.
  • Example 4 A bath was prepared similar to that in Example 3 except that it additionally contained 10.0 grams of sodium nitrate. The pH was 1.7. A zinc-plated test panel 2 inches x 3 inches was immersed therein for about twelve seconds with agitation and'then rinsed in cold water. The panel finish was bright and gave a surprisingly high test value of fifty-five seconds in the lead acetate test, indicating a very high degree of corrosion protection.
  • Example 5 i A bath was prepared by dissolving in one liter of water 5.6 grams of sodium bisulfate, 1.35 grams of sodium m'olybdate and 2-0.0 grams of sodium nitrate. The resultant pl-l was 1.0.
  • a Zinc-plated steel test panel 2 inches by 3 inches was immersed therein at room temperature with agitation for about twelve seconds and then rinsed in cold water.
  • the resultant finish was bright blue and gave a value of fifteen seconds in the lead acetate test, indicating a high degree of corrosion protection.
  • Example 6 A bath was prepared by dissolving 2.1 grams of sodium bifiuoride, 1.35 grams of sodium molybdate, "0 .14 gram of boric acid and 20.0 grams of urea nitrate in one liter of water.
  • a cadmium-plated steel panel 2 inches x 3 inches was immersedtherein with agitation for about ten seconds at room temperature and then rinsed in water.
  • the resultant finish was of yellowish, slightly iridescent hue and gave a value of six seconds in'the lead acetate test, indicating a fair measure of corrosion protection.
  • the present invention provides a novel composition and method for finishing zinc and cadmium surfaces to provide protection therefor which is relatively simple in operation.
  • the compositions of the present invention provide a single-dip bath for surface treating zinc andzinc-base alloys to provide a bright finish therefor which will give a high degree of corrosion protection.
  • a bath for treating zinc surfaces and cadmium surfaces comprising a dilute aqueous acid solution containing essentially about 0.2-6.5 grams per liter molybdate ion, 40-1000 grams per liter nitrate ion, and 01-150 grams per liter of an activating ion selected from the group consisting of fluoride and sulfate, said solution having a pH of about 0.5-2.2.
  • a bath for treating zinc surfaces comprising a dilute aqueous solution containing essentially 0.25-40 grams per liter of alkali metal molybdate, fluoride ion in a fluoride to molybdate weight ratio of about 1.4-1.8:1, and nitrate ion in a nitrate to molybd ate weight ratio of about 10-40:1, said solution having a pH of about 0.9-1.5.
  • a bath for treating zinc surfaces comprising a dilute aqueous solution containing essentially 0.5-8.0 grams per liter alkali metal molybdate, sulfate ion in a sulfate to molybdate weight ratio of about 1.5-2.0:1, and nitrate ion in a nitrate to molybdate weight ratio of about 10- 40:1, said solution having a pH of about 0.9-1.5.
  • a bath for treating zinc surfaces comprising a dilute aqueous solution containing essentially 025-40 grams per liter alkali metal molybdate, 0.5-12.0 grams per liter alkali metal-hydrogen fluoride and 4.5-75.0 cc. per liter nitric acid, said bath having a fluoride ion to molybdate ion ratio of about 1.4-1.8:1 and a nitrate ion to molybdate ion ratio of about -3021, said bath having a pH of about 0.9-1.5.
  • a self-contained dry powder formulation for addition to water to provide a bath for treating zinc surfaces and cadmium surfaces to impart corrosion protection thereto said formulation containing essentially about 2.0-8.0 percent by weight waiter-soluble alkali metal molybdate; 10-400 percent by weight of an water-soluble activing agent having an anion selected from the group consisting of sulfates and fluorides and a positive radical selected from the group consisting of alkali metalhydrogen, alkali metal and ammonium-hydrogen; up to 8.0 percent by weight of a water-soluble solid leveling agent having an anion selected from the group consisting of acetate and borate and a cation selected from the group consisting of hydrogen, alkali metal and ammonium; and 50.0-95.0 percent by weight of a water-soluble nitrate compound having a cation selected from the group consisting of alkali metal, urea and ammonium, at least one of said components being sufiiciently acidic in nature to provide a pH of 0.5-2.2
  • the dry powder formulation in accordance with claim 10 additionally containing up to 8.0 percent by weight of a water-soluble solid leveling agent having an anion selected from the group consisting of acetate and borate and a cation selected from the group consisting of hydrogen, alkali metal and ammonium.
  • a water-soluble solid leveling agent having an anion selected from the group consisting of acetate and borate and a cation selected from the group consisting of hydrogen, alkali metal and ammonium.
  • the method of treating zinc surfaces and cadmium surfaces to impart corrosion protection thereto compristing providing a dilute aqueous acid solution containing essentially about 0.2-6.5 grams per liter molybdate ion, 40-1000 grams per liter nitrate ion, and 0.1-15 .0 grams per liter of an activating ion selected from the group consisting of fluoride and sulfate, said solution having a pH of about 0.5-2.2; maintaining said solution at a temperature of about -120 degrees Fahrenheit; and immersing therein a workpiece having a surface selected from the group consisting of zinc surfaces and cadmium surfaces for a period of five to thirty seconds to develop corrosion protection thereon.

Description

United States Patent 3,171,766 BRIGHT POLISHING 9F CADMIUM AND ZINC Kenneth P. Bellinger, Ellington, Conn, assignor to Conversion Chemical Qorporation, Rockviile, Conn., a corporation of Connecticut No Drawing. Filed Oct. 4, 1962, Ser. No. 228,252 19 (Ilaims. (Cl. 156-20) The present invention relates to compositions and methods for finishing surfaces of cadmium, zinc and alloys thereof.
The term zinc surfaces as used herein refers to surfaces of zinc and zinc-base alloy articles and other metallic articles having a coating of zinc or zinc-base alloy such as produced by hot-dipping or electroplating.
The term cadmium surfaces as used herein refers to surfaces of cadmium and cadmium-base alloy articles and other metallic articles having a coating of cadmium or cadmium-base alloy such as produced by electroplating.
It is the aim of the present invention to provide a novel composition and method for finishing zinc surfaces and cadmium surfaces which is relatively simple in operation and provides protection therefor.
Another aim is to provide a simple and effective dilute single-dip composition and method for treating surfaces of zinc and zinc-base alloys to impart a bright finish thereto.
It is also an aim to provide a single-dip composition and method for surface-treating zinc and zinc-base alloys which give a high degree of corrosion protection in a bright or bright iridescent finish.
A further aim is to provide a self-contained dry powder composition for addition to water which will yield a bath for finishing zinc surfaces and cadmium surfaces to impart protection thereto.
It has now been found that the foregoing and related aims can be readily attained by immersing the zinc or cadmium workpiece in a dilute aqueous bath containing essentially molybdate ions, nitrate ions, and an activating ion selected from the group consisting of fluoride and sulfate, the bath having a pH of about 0.5-2.2 and preferably about 0.9-1.5. A leveling agent such as borate ion or acetate ion may also be incorporated to control the bath operation and produce increased clarity. The bath is maintained at ambient temperatures, and the workpiece is immersed therein for a period of about five to thirty seconds, preferably with agitation.
Generally, the dilute baths of the present invention contain essentially about 0.2-6.5 grams per liter molybdate ion, 4.0-1000 grams per liter of nitrate ion, {Ll-15.0 grams per liter of activating ion selected from the group consisting of fluoride and sulfate, and up to about 4.0 grams per liter of a leveling ion selected from the group consisting of borate and acetate. The nitrate ion should be maintained at a weight ratio relative to the molybdate ion in excess of about 10:1 to obtain desirable brightening but less than about 40:1 for desirable corrosion protection, and preferably on the order of 30:1.
By use of certain weight ratios of activating ion to molybdate ion, it has been found that good brightening action upon zinc can be readily attained through varying concentrations of the two components in the bath. When using the fluoride ion, it has been found desirable to utilize a fluoride to molybdate ion weight ratio of about 1.3-3zl, and preferably about 1.4-1.8:1. When using the sulfate ion, it has been found desirable to utilize a sulfate to molybdate weight ratio of about 0.5-2.0:1, and preferably about 0.7-1.2:1. Use of both sulfate and fluoride ions in a common bath formulation has been found generally to reduce the brightness of finish and, accordingly, only one of the activating ions should be employed 3,171,765 Patented Mar. 2, 1965 for optimum results. In practice, the fluoride ion baths appear to provide greatest brightness.
Leveling agents are desirably incorporated in the bath for pH control and control of the rate of bath action to achieve optimum brightening without the need for as critical control of times and temperatures. As little as 0.05 gram per liter will produce a beneficial effect, and amounts up to about one-third the weight of molybdate and activating ion, or about 4.0 grams per liter may be utilized, although the corrosion protection will generally be reduced by increasing concentration of the leveling ion. Accordingly, it is preferred to use only about 0.1-0.8 gram per liter for optimum brightening and corrosion protection. Borates and acetates have proven satisfactory as leveling agents.
The baths of the present invention have proven highly effective in providing both brightness and corrosion protection upon Zinc surfaces, the brighter finishes surprisingly demonstrating good corrosion protection, and the dull finishes generally exhibiting considerably lesser or no significant degree of corrosion protection as measured by the lead acetate test. 1 Although the present invention may be utilized to produce a bright finish upon cadmium surfaces under closely controlled conditions, generally there is produced a finish which varies from a cloudy film or yellow or blue iridescent to dull grey in appearance but which does provide some measure of corrosion protection. Accordingly, the present invention in its preferred aspect is directed to the treatment of zinc surfaces.
The several ions can be added to the bath as the acid or as salts which are soluble in water or acid solutions. However, since molybdic acid is relatively insoluble in both water and acid solutions, the alkali metal molybdates and particularly sodium molybdate have been advantageously employed.
Specific examples of finishing baths in accordance with the present invention and utilizing nitric acid are as follows:
FLUORIDE ION Range Optimum 0.25-4.13 g 1.0 g. 050- g 2.0 5:. Up to 4.0 g 0.15 g. 4.5-7.5.0 ce 18.0 on. To 1.0 liter To 1.0 liter.
SULFATE ION Range Optimum Alkali Metal illolybdate 0 5-8.0 g 2.0 g. Alkali Metal Bisulfate 0.5-8.0 2.0 g. Boric Acid Up to 5.0 g 0.15 g. Nitric Acid, 42 Baum (ill-100.0 ce 24.0 cc. Water To 1.0 liter To 1.0 liter.
By use of sufficient quantities of acidic salts to provide various of the component ions, a self-contained dry powder formulation can be prepared which will form the desired bath upon addition to water. Alkali metal-hydrogen and ammonium-hydrogen salts of fluoride and sulfate have been particularly useful as has urea nitrate for this purpose.
Generally, a dry powder formulation for addition to water contains essentially about 2.0-8.0 percent by weight alkali metal molybdate; 10-400 percent by weight of an A drop of an aqueous solution containing 5 percent by weight lead acetate is placed upon the surface and the time noted util the spot turns black. Generally 10 seconds is 111- dicative of a high measure of protection since an untreated panel will turn black immediately.
activatin a cut havin an anion selected from the roup D b O 1 consisting of sulfates and fluorides and a positive radical selected from the group consisting of alkali metal-hydrogen, alkali metal and ammonium-hydrogen; up to 8.0 percent by weight of a solid leveling agent having an anion selected from the group consisting of acetate and borate and a cation selected from the group consisting of hydrogen, alkali metal and ammonium; and '50.095.0 percent by weight of a nitrate compound having a cation selected from the groupconsistin'g of alkali metal, urea and amrnonium, at least one of said components being sufficiently acidic in nature to provide a pH of 0.52.2 upon addition of the composition to water in sufficient quantity to provide about 0.258.0 grams per liter of alkali metal molybdate.
V Specific examples of self-contained dry powder compositions in accordance with the present invention are as follows:
FLUO RIDE ION Either'type of dry powder formulation may be added .to water in amounts sulficient to provide the desired concentration of molybdate ion; i.e., about 0.26.5 grams per liter or about 025-80 grams per liter of alkali metal molybdate. Generally, this will require about 100-1000 grams of powder formulation per liter of water. 'T he pH of the resultant bath will vary with the concentration of the acidic component within the powder formulation and within the bath.
Generally, the baths of the present invention are employed at ambient temperatures of about 6590 degrees Fahrenheit and require immersion for short periods of about five to thirty seconds, preferably with mild agitation. However, low elevated temperatures of up to about 120 degrees Fahrenheit may be used, although with lesser control and shorter dip times. The workpieces are then rinsed in cold water.
Since the baths are corrosive, suitable tanks and handling equipment should be employed to avoid containina:
tion such as rigid polyvinyl chloride or glass fiber reinforced resin.
Exemplary of the efiicacy of the present invention are the following specific examples wherein test panels 2 inches x 3 inches were electroplated with zinc or cadmium and immersed in the several formulations under equivalent conditions of temperature, time and agitation.
Example 1 A bath was prepared by admixing 2.0 grams sodium acid fluoride, 1.35 grams sodium molybdate, 0.14 gram boric acid and 21.0 cc. of 42 Baum nitric acid in water to make 1.0 liter. The pH of the bath was measured at 1.35 using a reference solution of pH 1.1.
A steel test panel 2 inches x 3 inches having an electro plated zinc coating thereon was immersed in the bath at room temperature for about twelve seconds with agitation and then rinsed in cold water. The resultant finish was bright and free from iridescence. A drop of 5.0 percent by weight lead acetate solution did not turn the finish blacr for over twenty seconds, indicating a high degree of corrosion protection.
Example 2 Example '3 A bath was prepared by dissolving in one liter of water 2.0 grams of sodium-hydrogen fluoride, 1.35 grams of sodium molybdate, and 30.0 grams of urea nitrate. The resultant pH was 1.8.
A zinc-plated steel test panel Zinches x 3 inches was immersed therein at room temperature for about twelve seconds and then rinsed. The resultant finish was bright and gave a value of twenty seconds in the lead acetate test, indicating a high degree of corrosion protection.
Example 4 A bath was prepared similar to that in Example 3 except that it additionally contained 10.0 grams of sodium nitrate. The pH was 1.7. A zinc-plated test panel 2 inches x 3 inches was immersed therein for about twelve seconds with agitation and'then rinsed in cold water. The panel finish was bright and gave a surprisingly high test value of fifty-five seconds in the lead acetate test, indicating a very high degree of corrosion protection.
The addition of a further 10.0 grams of sodium nitrate produced a bath having a pH of 1.8 and resulted in a milky or cloudy finish upon the test panel. However, the value in the lead acetate test was not diminished.
Example 5 i A bath was prepared by dissolving in one liter of water 5.6 grams of sodium bisulfate, 1.35 grams of sodium m'olybdate and 2-0.0 grams of sodium nitrate. The resultant pl-l was 1.0.
A Zinc-plated steel test panel 2 inches by 3 inches was immersed therein at room temperature with agitation for about twelve seconds and then rinsed in cold water. The resultant finish was bright blue and gave a value of fifteen seconds in the lead acetate test, indicating a high degree of corrosion protection.
Example 6 A bath was prepared by dissolving 2.1 grams of sodium bifiuoride, 1.35 grams of sodium molybdate, "0 .14 gram of boric acid and 20.0 grams of urea nitrate in one liter of water.
A cadmium-plated steel panel 2 inches x 3 inches was immersedtherein with agitation for about ten seconds at room temperature and then rinsed in water. The resultant finish was of yellowish, slightly iridescent hue and gave a value of six seconds in'the lead acetate test, indicating a fair measure of corrosion protection.
Thus, it can be seen from the foregoing detailed specification and specific examples that the present invention provides a novel composition and method for finishing zinc and cadmium surfaces to provide protection therefor which is relatively simple in operation. The compositions of the present invention provide a single-dip bath for surface treating zinc andzinc-base alloys to provide a bright finish therefor which will give a high degree of corrosion protection. According to one aspect of the present invention, it is possible to provide a self-contained dry powder composition for addition to water to yield a Having thus described the invention, I claim:
1. A bath for treating zinc surfaces and cadmium surfaces comprising a dilute aqueous acid solution containing essentially about 0.2-6.5 grams per liter molybdate ion, 40-1000 grams per liter nitrate ion, and 01-150 grams per liter of an activating ion selected from the group consisting of fluoride and sulfate, said solution having a pH of about 0.5-2.2.
2. The bath in accordance with claim 1 wherein said solution contains a leveling ion selected from the group consisting of borate and acetate in an amount of about 0.05-4.0 grams per liter and not more than one-third the weight of the molybdate and activating ions.
3. The bath in accordance with claim 1 wherein the weight ratio of nitrate ion to molybdate ion is -40: 1.
4. The bath in accordance with claim 1 wherein the activating ion is fluoride and the fluoride to molybdalte weight ratio is 1.3-3.0:1.
5. The bath on accordance with claim 1 wherein the activating ion is sulfate and the sulfate to molybdate weight ratio is 0.5-2.0: 1.
6. The bath in accordance with claim 1 wherein the pH is about 0.9-1.5.
7. A bath for treating zinc surfaces comprising a dilute aqueous solution containing essentially 0.25-40 grams per liter of alkali metal molybdate, fluoride ion in a fluoride to molybdate weight ratio of about 1.4-1.8:1, and nitrate ion in a nitrate to molybd ate weight ratio of about 10-40:1, said solution having a pH of about 0.9-1.5.
8. A bath for treating zinc surfaces comprising a dilute aqueous solution containing essentially 0.5-8.0 grams per liter alkali metal molybdate, sulfate ion in a sulfate to molybdate weight ratio of about 1.5-2.0:1, and nitrate ion in a nitrate to molybdate weight ratio of about 10- 40:1, said solution having a pH of about 0.9-1.5.
9. A bath for treating zinc surfaces comprising a dilute aqueous solution containing essentially 025-40 grams per liter alkali metal molybdate, 0.5-12.0 grams per liter alkali metal-hydrogen fluoride and 4.5-75.0 cc. per liter nitric acid, said bath having a fluoride ion to molybdate ion ratio of about 1.4-1.8:1 and a nitrate ion to molybdate ion ratio of about -3021, said bath having a pH of about 0.9-1.5.
10. A self-contained dry powder formulation for addition to water to provide a bath for treating zinc surfaces and cadmium surfaces to impart corrosion protection thereto, said formulation containing essentially about 2.0-8.0 percent by weight waiter-soluble alkali metal molybdate; 10-400 percent by weight of an water-soluble activing agent having an anion selected from the group consisting of sulfates and fluorides and a positive radical selected from the group consisting of alkali metalhydrogen, alkali metal and ammonium-hydrogen; up to 8.0 percent by weight of a water-soluble solid leveling agent having an anion selected from the group consisting of acetate and borate and a cation selected from the group consisting of hydrogen, alkali metal and ammonium; and 50.0-95.0 percent by weight of a water-soluble nitrate compound having a cation selected from the group consisting of alkali metal, urea and ammonium, at least one of said components being sufiiciently acidic in nature to provide a pH of 0.5-2.2 upon addition of the composition to water in sufficient quantity to provide about 0.25- 8.0 grams per liter of alkali metal molybdate.
11. The dry powder formulation in accordance with claim 10 wherein the pH produced by said acidic component upon addition to water is 0.9-1.5.
12. The dry powder formulation in accordance with claim 10 wherein said nitrate compound is urea nitrate.
13. The dry powder formulation in accordance with claim 11 wherein said nitrate compound is in an amount providing a nitrate ion to molybdate ion ratio in the formulation of 10-4021.
14. The dry powder formulation in accordance with claim 10 additionally containing up to 8.0 percent by weight of a water-soluble solid leveling agent having an anion selected from the group consisting of acetate and borate and a cation selected from the group consisting of hydrogen, alkali metal and ammonium.
15. The dry powder formulation in accordance with claim 10 wherein the Weight ratio of nitrate ion to molybdate ion is 15-3011.
16. The method of treating zinc surfaces and cadmium surfaces to impart corrosion protection thereto compristing providing a dilute aqueous acid solution containing essentially about 0.2-6.5 grams per liter molybdate ion, 40-1000 grams per liter nitrate ion, and 0.1-15 .0 grams per liter of an activating ion selected from the group consisting of fluoride and sulfate, said solution having a pH of about 0.5-2.2; maintaining said solution at a temperature of about -120 degrees Fahrenheit; and immersing therein a workpiece having a surface selected from the group consisting of zinc surfaces and cadmium surfaces for a period of five to thirty seconds to develop corrosion protection thereon.
17. The method in accordance with claim 16 wherein said solution has a pH of 0.9-1.5.
18. The method in accordance with claim 16 wherein the weight ratio of nitrate ion to molybdate ion is 10- 40:1.
19. The method in accordance With claim 16 wherein said workpiece has a zinc surface and said solution provides a bright surface finish thereto.
References Cited in the file of this patent UNITED STATES PATENTS 2,186,579 Dupernell et al Jan. 9, 1940 2,377,593 Bunte June 5, 1945 2,904,413 Hampel Sept. 15, 1959 2,904,414 Ostrander et al Sept. 15, 1959 3,072,516 Bellinger et a1 Jan. 8, 1963

Claims (1)

16. THE METHOD OF TREATING ZINC SURFACES AND CADMIUM SURFACES TO IMPART CORROSION PROTECTION THERETO COMPRISING PROVIDING A DILUTE AQUEOUS ACID SOLUTION CONTAINING ESSENTIALLY ABOUT 0.2-6.5 GRAMS PER LITER MOLYBDATE ION, 4.0-100.0 GRAMS PER LITER NITRATE ION, AND 0.1-15.0 GRAMS PER LITER OF AN ACTIVATING ION SELECTED FROM THE GROUP CONSISTING OF FLUORIDE AND SULFATE, SAID SOLUTION HAVING A PH OF ABOUT 0.5-2.2; MAINTAINGING SAID SOLUTION AT A TEMPERATURE OF ABOUT 60-120 DEGREES FAHRENHEIT; AND IMMERSING THEREIN A WORKPIECE HAVING A SURFACE SELECTED FROM THE GROUP CONSISTING OF ZINC SURFACES AND CADMIUMN SURFACES FOR A PERIOD OF FIVE TO THIRTY SECONDS TO DEVELOP CORROSION PROTECTION THEREON.
US228252A 1962-10-04 1962-10-04 Bright polishing of cadmium and zinc Expired - Lifetime US3171766A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
US228252A US3171766A (en) 1962-10-04 1962-10-04 Bright polishing of cadmium and zinc

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US228252A US3171766A (en) 1962-10-04 1962-10-04 Bright polishing of cadmium and zinc

Publications (1)

Publication Number Publication Date
US3171766A true US3171766A (en) 1965-03-02

Family

ID=22856407

Family Applications (1)

Application Number Title Priority Date Filing Date
US228252A Expired - Lifetime US3171766A (en) 1962-10-04 1962-10-04 Bright polishing of cadmium and zinc

Country Status (1)

Country Link
US (1) US3171766A (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3314811A (en) * 1964-01-02 1967-04-18 Mitchell Bradford Chemical Co Metal treating compositions and processes
FR2820152A1 (en) * 2001-01-29 2002-08-02 Electro Rech Coloring of galvanizd metal components by dipping in a pH controlled chemical coloring bath

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2186579A (en) * 1933-06-28 1940-01-09 Udylite Corp Method of brightening metals electronegative to iron
US2377593A (en) * 1942-02-09 1945-06-05 Packard Motor Car Co Etching ink
US2904414A (en) * 1954-08-04 1959-09-15 Allied Res Products Inc Formulation for producing a protective bright chemically polished surface on zinc and cadmium
US2904413A (en) * 1954-06-23 1959-09-15 Jervis Corp Process of bright dipping zinc base alloys
US3072516A (en) * 1961-03-21 1963-01-08 Conversion Chem Corp Solution and method for brightening cadmium

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2186579A (en) * 1933-06-28 1940-01-09 Udylite Corp Method of brightening metals electronegative to iron
US2377593A (en) * 1942-02-09 1945-06-05 Packard Motor Car Co Etching ink
US2904413A (en) * 1954-06-23 1959-09-15 Jervis Corp Process of bright dipping zinc base alloys
US2904414A (en) * 1954-08-04 1959-09-15 Allied Res Products Inc Formulation for producing a protective bright chemically polished surface on zinc and cadmium
US3072516A (en) * 1961-03-21 1963-01-08 Conversion Chem Corp Solution and method for brightening cadmium

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3314811A (en) * 1964-01-02 1967-04-18 Mitchell Bradford Chemical Co Metal treating compositions and processes
FR2820152A1 (en) * 2001-01-29 2002-08-02 Electro Rech Coloring of galvanizd metal components by dipping in a pH controlled chemical coloring bath

Similar Documents

Publication Publication Date Title
US4298404A (en) Chromium-free or low-chromium metal surface passivation
US2796370A (en) Composition and method for producing corrosion resistant protective coating on aluminum and aluminum alloys
US2446060A (en) Chemical polishing of metal surfaces
KR100248163B1 (en) Zinc phosphate conversion coating composition and phosphating concentrates for coating metal surface
CA1200470A (en) Low zinc content, replenishment
US2106904A (en) Coating malleable non-noble heavy metals
JPS6136588B2 (en)
US2577887A (en) Activation of oxalate metal coating compositions
US2976193A (en) Process and compositions for producing aluminum surface conversion coatings
US3929514A (en) Composition and method for forming a protective coating on a zinc metal surface
US2121574A (en) Art of coating zinc
US2665231A (en) Coating process with alkali metal phosphate and added fluoride salt
US2904414A (en) Formulation for producing a protective bright chemically polished surface on zinc and cadmium
US4444601A (en) Metal article passivated by a bath having an organic activator and a film-forming element
US3072516A (en) Solution and method for brightening cadmium
US3843430A (en) Chromate-free bright dip for zinc and cadmium surfaces
US4490185A (en) Phosphating solutions and process
US3895969A (en) Composition and process for inhibiting corrosion of non-ferrous metal surfaced articles and providing surface for synthetic resin coating compositions
US2835617A (en) Composition and method for coating metallic surfaces
US3171767A (en) Composition and method for brightening cadmium and zinc
US3171766A (en) Bright polishing of cadmium and zinc
US3106484A (en) Metal treating
US3607453A (en) Metal treating process
US5244512A (en) Method for treating metal surface with zinc phosphate
US3338755A (en) Production of phosphate coatings on metals