CA1117405A - Testing chromium electroplating baths - Google Patents
Testing chromium electroplating bathsInfo
- Publication number
- CA1117405A CA1117405A CA000344047A CA344047A CA1117405A CA 1117405 A CA1117405 A CA 1117405A CA 000344047 A CA000344047 A CA 000344047A CA 344047 A CA344047 A CA 344047A CA 1117405 A CA1117405 A CA 1117405A
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- Prior art keywords
- ferrocyanide
- solution
- paper
- iron salt
- medium
- Prior art date
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Abstract
Trivalent chromium electroplating baths develop characteristic faults due to accumulation of trace metal contaminants. The presence of any excess of trace metal or of ferrocyanide may be detected by causing the solution to permeate upwardly through a water permeable medium and contacting separate parts of the solution in the water permeable medium with a soluble ferrocyanide and an iron salt respectively. Typically a test paper impregnated at either end with two salts is employed.
Description
1~7Df05 TESTING C~IROMIUM ELECTROPLATING BATHS
_. .
The present invention relates to the testing of chromium electroplating baths.
This application is a division of copending Canadian patent application Serial No. 256,190 filed July 2, 1976.
Although the potential advantages of electroplating from solutions containing chromium in the trivalent state have been recognized for over fifty years, until recently a variety of practical difficulties have prevented the commercial adoption of any such solution. Chromium has therefore always been electroplated from baths containing the chromium in the he avalent state, despite C~l L~i d~ an*aqeS
certain serious dic~av~t~g~of such baths.
Recently, however, various proposals have been made for overcoming at least some of the aforesaid difficulties.
One type of bath in particular, containing a trivalent chromium salt, a formate, a bromide and ammonium as essential ingredients is described in our U.S. Patent No. 3,954,574.
A process based on such a bath has recently been introduced commercially and is already gaining widespread acceptance as a replacement for hexavalent chromium plating baths.
However, it has been discovered that some trivalent chromium plating baths, which work satisfactorily under laboratory or test conditions, sometimes develop plating defects after they have been installed commercially. In particular at least one, and usually a combination, of the following faults may occur:
A. A white haze at high current densities, which may, in severe cases, spread progressively to lower current densities.
B. A white band at the lower limit of the plating range, often accompanied by loss of adhesion at high current densities.
C. A white deposit at current densities of around 50 amps per square foot.
D. Brown or black smudges between about 100 and 200 amps per square foot.
In accordance ~ith the invention defined in the parent application, the aforesaid faults, may, in many cases, be q~
~11740~
reduced or overcome by adding a small amount of water soluble fexrocyanide ~o the plating solution, whenever the faults are observed.
The invention of the parent case has been found to be applicable to the maintenance of trivalent chromium electroplating baths generally. For example, it may be employed with baths of the type described in our aforesaid U.S. patent, or with baths containing glycollic acid such as are described in U.S. Patents Nos. 3,706,636 to 643. The invention may also be used, for example, in combination with baths of the type described in British Patent No.
1,144,~13, U.S. Patent No. 3,021,267, U.S. Patent No.
3,006,823, U.S. Patent No. 3,Q69,333 and U.S. Patent No.
3,111,464~
Generally speaking the baths contain a trivalent chromium salt, such as chromium chloride, sulphate or fluoride and a complexing agent such as a carboxylic acid, preferably a formate, or alternatively, for example, an acetate, glycollate or oxalate. Halides especially bromide are preferably present. The solution preferably contains alkali metal ions, for example sodium and/or potassium, and sulphate ions. Aprotic dipolar solvents such as dimethyl formamide may also be included but are preferably absent. Typically the pH of the bath is between 1 and 7, for example 1.5 to 5.
The ferrocyanide may be any ferrocyanide which is soluble in the bath, for example an alkali metal or ammonium ferrocyanide, for example sodium or potassium ferrocyanide.
The ferrocyanide may conveniently be added to the bath as an aqueous solution. The concentration of the ferrocyanide solution is not critical, and will normally be chosen according to the solubility of the particular ferrocyanide employed. For example using potassium ferro-cyanide we prefer to employ a solution containing about 20 by weight ferrocyanide.
Addition of ferroc~anide in amounts in excess of those required to eliminate the aforesaid faults, may cause a deterioration in the performance of the bath. One way of av~i~ng ~s pr~bl~m whe~ th~ onset of any of the aforesaid faults is obse~d, is to add the fernx~anide solution in small incr~ts until the chromium deposit is satisfactory again. If a sufficient excess of ferrocyanide has accidentally been added to cause a significant deterioration, it is possible to remove the excess by adding a small amount of soluble cation such as copper, nickel, iron or zinc. In most plating shops this may conveniently be achieved by adding a small amount of nickel plating solutior. to the bath. The addition of metal ion should be made within 15 minutes preferably wit~in 10 minutes of adding the ferrocyanide, in order to be fully effective~ since on standing the excess ferrocyanide complexes with the chromium and is then difficult or impossible to precipitate with the added metal.
We believe that the aforesaid faults may be due to the accidental contamination of the bath by traces of metal cations, which are capable of codepositing with the chromium.
Our experiments have shown that fault A can be simulated by adding copper to the bath; similarly fault B appears to 20 be associated with the presence of zinc, fault C with lead and fault D with nickel or a mixture of nickel and iron.
It seems, surprisingly, that the ferrocyanide is capable of precipitating substantially all of the potentially harm-ful trace metals which are most commonly encountered in 25 very low concentrations as contaminan~s in commercial practice, but without precipitating the chromiumt which is ~;A a principal cationic ~ of the bath.
Analysis of the bath to determine the concentration of trace metal contaminants therein may be carried out by any of the analytir~l techniques for quantitative determination of the trace metals which are well known in the art. Typically the bath may be analyzed by spectographic means, for example by spark ionization or atomic absorption. Alternatively polarographic means may be employed.
Usually it is only necessary to test for copper, zinc, iron and nickel, since these are the only metals which, in our experience, are likely to cause difficulties in practice. The invention is however applica~le to the coxrection of plating faults due to the presence of other ~1~74(~5 codepositable metals, including lead, cadmium, silver and gold, although significant contamination by such metals is unlikely to occur in practice.
The amount of ferrocyanide added is preferably substantially stoichiometric based on the trace metal contaminants present, or slightly less. Any substantial excess of ferrocyanide should be avoided. Addition of any effective quantity significantly less than the stoichiometric amount, while beneficial, may not entirely remove the plating fault. A good rule of thumb is to add 1 ml. of 20~ potassium ferrocyanide solution per litre of plating solution for every 50 ppm of trace metal contamination. In this way the bath can be relatively easily maintained in the face of at least the commonly encountered forms of contamination.
It is preferred to reduce any free halogen in the bath to halide prior to addition of the ferrocyanide, by addition of a reducing agent capable of converting halogen to halide, without adversely affecting the performance of the bath. One particularly suitable reducing agent for this purpose is ammonium formate, The proportion of formate is preferably sufficient to reduce all the free halogen in the solution. Typically 2 to 3 gms per litre of formate may be added, preferably as an aqueous solution.
The formate is preferably added with agitation, about 10 minutes prior to the ferrocyanide addition. Halogen is usually present in the bath immediately after plating.
The present invention provides a rapid method for detecting the presence of harmful excesses of either the ferrocyanide or certain of the commoner metallic impurities, so that appropriate remedial action can be taken withou~
delay.
According to the present invention, there is provided a method of testing a trivalent chromium plating bath to determine the presence of an excess of either a ferrocyanide or metallic impurity therein, which comprises contacting the solution with a water permeable medium, causing the solution to diffuse upwardly through the medium,and contact-ing separate portions of the diffusing solution in the li~74~5 medium with a water soluble ferrocyanide salt and with a water soluble iron salt respectively.
Typically the contact between the diffusing solution ancl the two salts is ensured by impregnating separate parts of the medium with the two salts, the impregnated parts bei.ng disposed in such a way as to intercept separa~e por tions of the diffusing solution. Preferably impregnated parts should be readily visible to an external observer so as to facilitate the detection of any colour changes.
The permeable medium is preferably a cellulosic material such as filter paper or chromatography paper.
However, any medium which is capable of causing aqueous solutions to diffuse upwardly therethrough, when its lower part is immersed, may in principle be employed. Preferably the medium is substantially colourless so as to permit observation of small colour changes.
Preferably the medium is a water permeable paper.
A particularly convenient form of test paper used in this 2Q invention comprises a strip of permeable paper, such as, filter paper, which can, for example, be rectangular or any similar convenient shape, a part at or near one end of which has been impregnated with the ferrocyanide and a part at or near the other end of which has been impregnated with the iron salt, preferably leaving an unimpregnated central part between the two impregnated parts. In use, such a paper may be bent or folded about the unimpregnated part, so as to permit the latter to be contacted with the solution, leaving the two impregnated parts unimmersed. The solution diffused up each immersed arm of the paper, which separates out suspended solids, so enabling any colour change in either arm to be more readily detected.
Test papers of this type may conveniently ~e obtained by preparing rectangular strips of permeable paper and immersing the two ends of each strip respectively in solutions of the two salts, for sufficient time to permit the two solutions to diffuse into separate, preferably non-overlapping parts of the paper. The paper may then be dried, for example in an oven.
The tests effecting according to this invention may alt~tively be perfo ~ d using tw~ separate test papers impregnated respectively with the two salts. If the medium is non-coherent or brittle in nature a suitable support means may be provided. For example, it is possible to perform the tests using a thin layer of silica gel supported on a plate, or in the case of powdery or gelatinous media, to support the medium in a column (preferably of glass or similar transparent material).
The ferrocyanide salt is preferably an alkali metal or ammonium ferrocyanide for example tetra potassium ferrocyanide. The iron salt may be a ferric or preferably a ferrous salt, preferably of a mineral acid, for example a chloride, nitrate or sulphate.
If a blue stain forms on contact between the solution being tested and the ferrocyanide, then the solution contains an excess of the metallic impurities, whereas a blue stain forming on contact between the solution and the iron salt indicates an excess of ferrocyanide. Preferably an aliquot 2Q of trivalent chromium plating solution is taken and ferro-cyanide is added, stepwise, thereto. The solution is checked after each addition with the test paper. The end point, in mls. ferrocyanide per litre of plating solution represents a maximum. In practice, preferably about 50%
of this amount of ferrocyanide is added to the bath, followed by a further addition of e.g. 25%, if required.
The invention will be illustrated by the following Examples:
Example 1 Test papers were each prepared by dipping one end of a rectangular strip of filter paper in 2a% w/v solution of tetra potassium ferrocyanide and the other end is a 20~ w/v solution of ferrous chloride. The solutions were each allowed to diffuse part way towards the centre of the strip, which was then dried in an oven.
Example 2 A trivalent chromium plating solution, after working satisfactorily for several weeks, developed a fault which 1~17~5 comprised the formation of dark smudges at current densities of between 100 and 200 amps per square foot. A test paper prepared according to Example l was folded across the unimpregnated central portion, which was dipped in the bath. The electrolyte diffused towards both ends of the paper and produced a blue stain near the ferrocyanide impregnated end, indicating the presence of metallic impurities. ~/~
A 10%~aqueous solution of tetra potassium ferrocyanide O was added in 4 ml increments, allowing 30 minutes after~
each addition and then repeating the test. After the second addition, a blue stain was observed at the iron impregnated end of the paper. 2 ml of 20% w/v ferrous chloride solution was added whereafter no stain was observed. Commercial plating was resumed and the bath functioned satisfactorily.
_. .
The present invention relates to the testing of chromium electroplating baths.
This application is a division of copending Canadian patent application Serial No. 256,190 filed July 2, 1976.
Although the potential advantages of electroplating from solutions containing chromium in the trivalent state have been recognized for over fifty years, until recently a variety of practical difficulties have prevented the commercial adoption of any such solution. Chromium has therefore always been electroplated from baths containing the chromium in the he avalent state, despite C~l L~i d~ an*aqeS
certain serious dic~av~t~g~of such baths.
Recently, however, various proposals have been made for overcoming at least some of the aforesaid difficulties.
One type of bath in particular, containing a trivalent chromium salt, a formate, a bromide and ammonium as essential ingredients is described in our U.S. Patent No. 3,954,574.
A process based on such a bath has recently been introduced commercially and is already gaining widespread acceptance as a replacement for hexavalent chromium plating baths.
However, it has been discovered that some trivalent chromium plating baths, which work satisfactorily under laboratory or test conditions, sometimes develop plating defects after they have been installed commercially. In particular at least one, and usually a combination, of the following faults may occur:
A. A white haze at high current densities, which may, in severe cases, spread progressively to lower current densities.
B. A white band at the lower limit of the plating range, often accompanied by loss of adhesion at high current densities.
C. A white deposit at current densities of around 50 amps per square foot.
D. Brown or black smudges between about 100 and 200 amps per square foot.
In accordance ~ith the invention defined in the parent application, the aforesaid faults, may, in many cases, be q~
~11740~
reduced or overcome by adding a small amount of water soluble fexrocyanide ~o the plating solution, whenever the faults are observed.
The invention of the parent case has been found to be applicable to the maintenance of trivalent chromium electroplating baths generally. For example, it may be employed with baths of the type described in our aforesaid U.S. patent, or with baths containing glycollic acid such as are described in U.S. Patents Nos. 3,706,636 to 643. The invention may also be used, for example, in combination with baths of the type described in British Patent No.
1,144,~13, U.S. Patent No. 3,021,267, U.S. Patent No.
3,006,823, U.S. Patent No. 3,Q69,333 and U.S. Patent No.
3,111,464~
Generally speaking the baths contain a trivalent chromium salt, such as chromium chloride, sulphate or fluoride and a complexing agent such as a carboxylic acid, preferably a formate, or alternatively, for example, an acetate, glycollate or oxalate. Halides especially bromide are preferably present. The solution preferably contains alkali metal ions, for example sodium and/or potassium, and sulphate ions. Aprotic dipolar solvents such as dimethyl formamide may also be included but are preferably absent. Typically the pH of the bath is between 1 and 7, for example 1.5 to 5.
The ferrocyanide may be any ferrocyanide which is soluble in the bath, for example an alkali metal or ammonium ferrocyanide, for example sodium or potassium ferrocyanide.
The ferrocyanide may conveniently be added to the bath as an aqueous solution. The concentration of the ferrocyanide solution is not critical, and will normally be chosen according to the solubility of the particular ferrocyanide employed. For example using potassium ferro-cyanide we prefer to employ a solution containing about 20 by weight ferrocyanide.
Addition of ferroc~anide in amounts in excess of those required to eliminate the aforesaid faults, may cause a deterioration in the performance of the bath. One way of av~i~ng ~s pr~bl~m whe~ th~ onset of any of the aforesaid faults is obse~d, is to add the fernx~anide solution in small incr~ts until the chromium deposit is satisfactory again. If a sufficient excess of ferrocyanide has accidentally been added to cause a significant deterioration, it is possible to remove the excess by adding a small amount of soluble cation such as copper, nickel, iron or zinc. In most plating shops this may conveniently be achieved by adding a small amount of nickel plating solutior. to the bath. The addition of metal ion should be made within 15 minutes preferably wit~in 10 minutes of adding the ferrocyanide, in order to be fully effective~ since on standing the excess ferrocyanide complexes with the chromium and is then difficult or impossible to precipitate with the added metal.
We believe that the aforesaid faults may be due to the accidental contamination of the bath by traces of metal cations, which are capable of codepositing with the chromium.
Our experiments have shown that fault A can be simulated by adding copper to the bath; similarly fault B appears to 20 be associated with the presence of zinc, fault C with lead and fault D with nickel or a mixture of nickel and iron.
It seems, surprisingly, that the ferrocyanide is capable of precipitating substantially all of the potentially harm-ful trace metals which are most commonly encountered in 25 very low concentrations as contaminan~s in commercial practice, but without precipitating the chromiumt which is ~;A a principal cationic ~ of the bath.
Analysis of the bath to determine the concentration of trace metal contaminants therein may be carried out by any of the analytir~l techniques for quantitative determination of the trace metals which are well known in the art. Typically the bath may be analyzed by spectographic means, for example by spark ionization or atomic absorption. Alternatively polarographic means may be employed.
Usually it is only necessary to test for copper, zinc, iron and nickel, since these are the only metals which, in our experience, are likely to cause difficulties in practice. The invention is however applica~le to the coxrection of plating faults due to the presence of other ~1~74(~5 codepositable metals, including lead, cadmium, silver and gold, although significant contamination by such metals is unlikely to occur in practice.
The amount of ferrocyanide added is preferably substantially stoichiometric based on the trace metal contaminants present, or slightly less. Any substantial excess of ferrocyanide should be avoided. Addition of any effective quantity significantly less than the stoichiometric amount, while beneficial, may not entirely remove the plating fault. A good rule of thumb is to add 1 ml. of 20~ potassium ferrocyanide solution per litre of plating solution for every 50 ppm of trace metal contamination. In this way the bath can be relatively easily maintained in the face of at least the commonly encountered forms of contamination.
It is preferred to reduce any free halogen in the bath to halide prior to addition of the ferrocyanide, by addition of a reducing agent capable of converting halogen to halide, without adversely affecting the performance of the bath. One particularly suitable reducing agent for this purpose is ammonium formate, The proportion of formate is preferably sufficient to reduce all the free halogen in the solution. Typically 2 to 3 gms per litre of formate may be added, preferably as an aqueous solution.
The formate is preferably added with agitation, about 10 minutes prior to the ferrocyanide addition. Halogen is usually present in the bath immediately after plating.
The present invention provides a rapid method for detecting the presence of harmful excesses of either the ferrocyanide or certain of the commoner metallic impurities, so that appropriate remedial action can be taken withou~
delay.
According to the present invention, there is provided a method of testing a trivalent chromium plating bath to determine the presence of an excess of either a ferrocyanide or metallic impurity therein, which comprises contacting the solution with a water permeable medium, causing the solution to diffuse upwardly through the medium,and contact-ing separate portions of the diffusing solution in the li~74~5 medium with a water soluble ferrocyanide salt and with a water soluble iron salt respectively.
Typically the contact between the diffusing solution ancl the two salts is ensured by impregnating separate parts of the medium with the two salts, the impregnated parts bei.ng disposed in such a way as to intercept separa~e por tions of the diffusing solution. Preferably impregnated parts should be readily visible to an external observer so as to facilitate the detection of any colour changes.
The permeable medium is preferably a cellulosic material such as filter paper or chromatography paper.
However, any medium which is capable of causing aqueous solutions to diffuse upwardly therethrough, when its lower part is immersed, may in principle be employed. Preferably the medium is substantially colourless so as to permit observation of small colour changes.
Preferably the medium is a water permeable paper.
A particularly convenient form of test paper used in this 2Q invention comprises a strip of permeable paper, such as, filter paper, which can, for example, be rectangular or any similar convenient shape, a part at or near one end of which has been impregnated with the ferrocyanide and a part at or near the other end of which has been impregnated with the iron salt, preferably leaving an unimpregnated central part between the two impregnated parts. In use, such a paper may be bent or folded about the unimpregnated part, so as to permit the latter to be contacted with the solution, leaving the two impregnated parts unimmersed. The solution diffused up each immersed arm of the paper, which separates out suspended solids, so enabling any colour change in either arm to be more readily detected.
Test papers of this type may conveniently ~e obtained by preparing rectangular strips of permeable paper and immersing the two ends of each strip respectively in solutions of the two salts, for sufficient time to permit the two solutions to diffuse into separate, preferably non-overlapping parts of the paper. The paper may then be dried, for example in an oven.
The tests effecting according to this invention may alt~tively be perfo ~ d using tw~ separate test papers impregnated respectively with the two salts. If the medium is non-coherent or brittle in nature a suitable support means may be provided. For example, it is possible to perform the tests using a thin layer of silica gel supported on a plate, or in the case of powdery or gelatinous media, to support the medium in a column (preferably of glass or similar transparent material).
The ferrocyanide salt is preferably an alkali metal or ammonium ferrocyanide for example tetra potassium ferrocyanide. The iron salt may be a ferric or preferably a ferrous salt, preferably of a mineral acid, for example a chloride, nitrate or sulphate.
If a blue stain forms on contact between the solution being tested and the ferrocyanide, then the solution contains an excess of the metallic impurities, whereas a blue stain forming on contact between the solution and the iron salt indicates an excess of ferrocyanide. Preferably an aliquot 2Q of trivalent chromium plating solution is taken and ferro-cyanide is added, stepwise, thereto. The solution is checked after each addition with the test paper. The end point, in mls. ferrocyanide per litre of plating solution represents a maximum. In practice, preferably about 50%
of this amount of ferrocyanide is added to the bath, followed by a further addition of e.g. 25%, if required.
The invention will be illustrated by the following Examples:
Example 1 Test papers were each prepared by dipping one end of a rectangular strip of filter paper in 2a% w/v solution of tetra potassium ferrocyanide and the other end is a 20~ w/v solution of ferrous chloride. The solutions were each allowed to diffuse part way towards the centre of the strip, which was then dried in an oven.
Example 2 A trivalent chromium plating solution, after working satisfactorily for several weeks, developed a fault which 1~17~5 comprised the formation of dark smudges at current densities of between 100 and 200 amps per square foot. A test paper prepared according to Example l was folded across the unimpregnated central portion, which was dipped in the bath. The electrolyte diffused towards both ends of the paper and produced a blue stain near the ferrocyanide impregnated end, indicating the presence of metallic impurities. ~/~
A 10%~aqueous solution of tetra potassium ferrocyanide O was added in 4 ml increments, allowing 30 minutes after~
each addition and then repeating the test. After the second addition, a blue stain was observed at the iron impregnated end of the paper. 2 ml of 20% w/v ferrous chloride solution was added whereafter no stain was observed. Commercial plating was resumed and the bath functioned satisfactorily.
Claims (16)
1. A method for testing a trivalent chromium electro-plating bath to determine the presence of an excess of either a ferrocyanide or metallic impurity therein, which comprises contacting the solution with a water permeable medium, causing the solution to diffuse upwardly through the medium, and contacting separate portions of the diffusing solution in the medium with a water soluble ferrocyanide salt and with a water soluble iron salt respectively.
2. The method of claim 1, wherein the contact between the diffusing solutions of the two salts is achieved by impregnating separate parts of the medium with the two salts respectively and disposing the impregnated parts in such a way as to intercept separate portions of the diffusing solution.
3. The method of claim 1 wherein the permeable medium is a cellulosic material.
4. The method of any one of claims 1 to 3 wherein said permeable medium is substantially colourless.
5. The method of any one of claims 1 to 3 wherein the permeable medium is a water permeable paper.
6. The method of any one of claims 1 to 3 wherein the ferrocyanide is sodium, potassium or ammonium ferrocyanide.
7. The method of claim 1 wherein said permeable medium is substantially colourless and the ferrocyanide is sodium, potassium or ammonium ferrocyanide.
8. The method of claim 1 wherein said permeable medium is a water-permeable paper and the ferrocyanide is sodium, potassium or ammonium ferrocyanide.
9. The method of any one of claims 1 to 3 wherein the iron salt is a ferrous salt of a strong mineral acid.
10. The method of claim 1 wherein said permeable medium is substantially colourless and the iron salt is a ferrous salt of a strong mineral acid.
11. The method of claim 1 wherein said permeable medium is a water permeable paper and the iron salt is a ferrous salt of a strong mineral acid.
12. The method of any one of claims 1 to 3 wherein said test is effected by means of a strip of filter paper impregnated at either end with a ferrocyanide and an iron salt respectively, bending said filter paper about a central unimpregnated portion and contacting the bent portion with the solution so that the latter diffuses upwardly towards each end of the paper.
13. The method of claim 7 or 8, wherein said test is effected by means of a strip of filter paper impregnated at either end with a ferrocyanide and an iron salt respectively, bending said filter paper about a central unimpregnated portion and contacting the bent portion with the solution so that the latter diffuses upwardly towards each end of the paper.
14. The method of claim 10 or 11, wherein said test is effected by means of a strip of filter paper impregnated at either end with a ferrocyanide and an iron salt respectively, bending said filter paper about a central unimpregnated portion and contacting the bent portion with the solution so that the latter diffuses upwardly towards each end of the paper.
15. The method of claim 1 wherein said test is effected by means of a strip of filter paper impregnated at either end with a ferrocyanide and an iron salt respectively, bending said filter paper about a central unimpregnated portion and contacting the bent portion with the solution so that the latter diffuses upwardly towards each end of the paper, and said ferrocyanide is sodium, potassium or ammonium ferrocyanide, and the iron salt is a ferrous salt of a strong mineral acid.
16. The method of claim 1 wherein the ferrocyanide is sodium, potassium or ammonium ferrocyanide and the iron salt is a ferrous salt of a strong mineral acid.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000344047A CA1117405A (en) | 1975-07-03 | 1980-01-21 | Testing chromium electroplating baths |
Applications Claiming Priority (7)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB28055/75A GB1558169A (en) | 1975-07-03 | 1975-07-03 | Chromium electroplating |
| GB28055/75 | 1975-07-03 | ||
| GB51801/75 | 1975-12-18 | ||
| GB5180175 | 1975-12-18 | ||
| CA256,190A CA1084441A (en) | 1975-07-03 | 1976-07-02 | Chromium electroplating |
| KR7603197A KR800001242B1 (en) | 1975-12-18 | 1976-12-28 | Chromium electroplating |
| CA000344047A CA1117405A (en) | 1975-07-03 | 1980-01-21 | Testing chromium electroplating baths |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1117405A true CA1117405A (en) | 1982-02-02 |
Family
ID=27508067
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000344047A Expired CA1117405A (en) | 1975-07-03 | 1980-01-21 | Testing chromium electroplating baths |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1117405A (en) |
-
1980
- 1980-01-21 CA CA000344047A patent/CA1117405A/en not_active Expired
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