JPH02258981A - Lead-tin plating composition - Google Patents

Abstract

PURPOSE: To provide the aq. acidic soln. compsn. which is prepd. by adding an effective amt. of a hydroxylamine agent to an aq. acidic copper-tin bath and uniquely improves the colors of copper-tin coatings by electroless plating the surface of iron metals with these coatings.

CONSTITUTION: This compsn. for copper and tin plating contains about 0.25 to about 0.65wt.% copper ions, about 0.25 to about 0.6wt.% tin ions and the effective amt. of the hydroxylamine agent. The copper ion source described above is preferably copper sulfate and tin metals, tin benzoate, etc., are used as the tin ion source. Hydroxylamine, phosphate, etc., are used as the hydroxylamine agent. If the weight ratio of the copper and the tin is set at about 2.0 to about 0.5, the coatings of the improved bronze color are obtd. The pH range preferable for the bath or the soln. to be used is a range of about 0 to about 4 and more particularly about 0.2 to about 2.0.

COPYRIGHT: (C)1990,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an acidic aqueous solution composition used in electroless plating of a ferrous metal surface with a copper/tin coating, and a method of using the same.

[Conventional technology]

Many processing solutions have been proposed for forming copper-tin plating on metal surfaces without the use of electrical current.

Those solutions that are often used are solutions of copper and tin sulfates combined with one or more additives that serve to promote the adhesion of the copper-tin plating and/or to improve the properties of the resulting plating. It is an acidic aqueous solution of inorganic copper and tin salts. It has been recognized that higher levels of tin are desirable in such solutions.

U.S. Patent No. 3.73, issued May 29, 1973
6, 157, copper ions in the range of about 0.01 to 0.30% by weight, calculated as CuSO4.5H20, and about 0.1 to 0.3%, calculated as SnSO4.
Aqueous acidic compositions for coating ferrous metal surfaces are described containing tin ions in the range of 0% by weight and long chain aliphatic amines in the range of about 0.01-0.10% by weight.

U.S. Patent No. 3.43, issued March 11, 1969
No. 2,337 discloses C in a weight ratio of 2:1 to 1:2.
uS O4・5 Hto and S n S O<, and 0
Aqueous solutions for coating ferrous metal surfaces are described containing polyaminopolycarboxylic acids ranging from .01 to 0.15% by weight.

U.S. Patent No. 3.3, issued October 10, 1967
No. 46.404 describes an aqueous acidic sulfate solution containing stannous ions, copper ions, and certain amino acids, including glutamic acid, ascorbic acid, and glycic acid, for coating ferrous metal surfaces. ing.

Although these compositions generally provide satisfactory results, they have encountered some difficulties associated with maintaining free Sn'' ions in solution. Sn″2 ions often oxidize automatically to Sn″,
The oxidation of tin to its insoluble salt reduces the effectiveness of the bath, resulting in insoluble Sn(S O4)2, which is useless in the coating bath. Since pan and tin salts are relatively expensive, the oxidation of tin to its insoluble salts makes the entire process more costly.

It is known in the art to use hydroxylamine in other types of coating solutions.

U.S. Patent No. 2.2, published October 13, 1942.
No. 98,280 describes the use of hydroxylamine as an accelerator in phosphate coating solutions to promote the adhesion of phosphate coatings based on corrosion-resistant paints.

U.S. Patent No. 2.70, issued February 22, 1955.
No. 2,768 specifies sodium, potassium 1. The use of droxylamine in "uncoated phosphate" solutions, such as those containing phosphates of ammonium and ammonium, has been described.

U.S. Patent No. 2.92, issued March 15, 1960.
No. 8.762 describes the use of hydroxylamine phosphate as a reducing agent in an orthophosphoric acid prerinse solution in a phosphate coating process.

U.S. Patent No. 4.00, issued January 18, 1977
No. 3,761 describes a method for applying phosphate coatings to iron surfaces. The method consists of spraying onto the surface an acidic aqueous solution having a pH of 4.3 to 6.5 and containing alkali metal or ammonium salts. The solution may further contain an oxidizing agent or reducing agent promoter, 0.05-1.0 g/l.
C, -C, alkylolamine and wetting agent.

U.S. Patent No. 4.14, issued April 17, 1979
No. 9,909 describes accelerated phosphorylation compositions containing hydroxylamine sulfate (as the source of hydroxylamine in the use solution) to provide a combination of hydroxylamine plus chlorate/bromate promoters.

U.S. Patent No. 4.220, issued September 2, 1980
, 486, optionally contains a pyrazole, hydroxylamine or hydrazine compound at 0.2 to 5.0 f/1.
A conversion coating solution with a pH of 5, 5 to 6.5 was used. These compounds are added to stabilize the working solution.

It is thus recognized in the art that hydroxylamine or hydroxylamine salts or complexes can be used to promote the adhesion of coatings intended to serve as paint bases or corrosion protection bases.

[Summary of the invention]

The present invention relates to an aqueous acidic steel/tin bath containing an increased amount of free Sn''2 ions.Advantages and advantages of the present invention include the addition of an effective amount of a hydroxylamine agent to an aqueous acidic steel/tin bath. This is achieved by

In the practice of this invention, aqueous acidic compositions useful for forming copper-tin coatings on ferrous metal surfaces without the application of electrical current contain copper ions, tin ions, and hydroxylamine. In a preferred embodiment, copper ions are present at a level ranging from about 0.25 to about 0.6 weight percent (measured as Cu+2) and tin ions are present at a level ranging from about 0.15 to about 0.6 weight percent (S
n+2), and the hydroxylamine agent is present in an effective amount, preferably about 0.01
to about 0.4% by weight (measured as the weight of the hydroxylamine source as described herein) and optionally an aliphatic amine in the range of about 0.05 to 0.20% by weight. exist.

Prior to coating, the metal article may be subjected to one or more conventional pretreatment steps, such as cleaning, pickling, rinsing, etc., prior to conventional processing or forming operations, prior to coating. The article may be subjected to one or more conventional post-treatment steps such as neutralization, rinsing, drying, and the like.

Additional advantages and advantages of the invention will become apparent from reading the detailed description of the invention in conjunction with the specific embodiments given.

[Detailed description of the invention]

treating various types of ferrous metal surfaces with the compositions and use solutions or baths of the invention without the use of electrical current;
It has been found that improved bright adhesive steel-tin alloy coatings can be formed on ferrous metal surfaces. Furthermore, good results can be obtained even when the ferrous ion content in the working solution or liquid is close to the saturation point. It has been found to be particularly suitable for processing that line. It has been found that the resulting copper-tin alloy coating remains adhered even after the drawing operation.

In particular, the novel use solution or bath composition of the present invention is an acidic aqueous solution containing steel ions, tin ions and a hydroxylamine agent. In preferred embodiments, the solutions contain copper ions, calculated as Cu+2, in the range of about 0.25 to about 0.6, preferably about 0.30 to about 0.45, by weight. Copper ions can be incorporated into the use solution or solution in any suitable source or form, such as copper metal and/or various copper salts. Whatever the source or form of the copper ions, the final acidic plating solution will contain the desired copper ion content (within the effective 9H range defined herein).
and that other anions or cations contained within the copper salt have no material detrimental effect on the effectiveness of the solution or the overall quality of the copper-tin plating produced. All that is required is what is said.

In many cases, it has been found that the use of sulfated steel as a source of copper ions in forming the acidic working solutions or baths of the present invention is a no-brainer. If the aqueous acidic plating bath used contains such sulfate ions, they will range from about 0.3% to about 20% by weight of the solution, preferably about 1.0% by weight of the solution.
It is typically present at a level or amount ranging from about 10% by weight. It will of course be appreciated that other copper salts such as copper metaborate, copper sulfamate, etc. may be used as a source of copper ions, but if such other salts or acids are used, their It will also be appreciated that care must be taken to ensure that the amount of other ions introduced, such as, does not exceed the maximum amount that can be present in solution without substantial deleterious effects.

It will be appreciated that the tin ions, like the copper, may be introduced into the baths or solutions of the invention from any suitable source or in any suitable form.

Such sources or forms would include tin metal, tin benzoate, tin metaborate, tin sulfamate, etc., again with the attendant anions or other contained within the tin salt. It is only necessary that the cations have no substantial detrimental effect on the effectiveness of the solution or the overall quality of the copper-tin plating produced.

The improved plating bath or use solution of the present invention also includes a hydroxylamine composition or source.

The unique properties of the coating used in this invention result from the coating being deposited from a hydroxylamine-containing steel-tin coating solution. Hydroxylamine may be added to the coating solution from any suitable conventional source; therefore, the term "hydroxylamine agent" as used herein refers to the hydrogen, hydroxylamine agent or source. is a storage-stable hydroxylamine salt, complex or derivative. Many of them are commercial items and often exist in hydrated form. These include hydroxylamine phosphate, nitrate, sulfate or mixtures thereof. A hydrazine salt may be used; the hydroxylamine agent or source is more preferably a coating concentrate formulated with hydroxylamine sulfate, a stable salt of hydroxylamine; the hydroxylamine sulfate has the formula (N H to H
)2H2SO4 or (NHiOH)iso4, hydroxylamine IEM (NH20HH
, 5O4) may be used in the present invention.

Effective amounts of hydroxylamine from any source can be used in these coatings.

As used herein, the term "effective amount" refers to a sufficient amount of hydroxylamine agent (regardless of the source) to prevent the amount of free Sn''2 in the coating from being reduced over time by automatic oxidation. That is, when comparing two substantially similar copper-tin coating baths, the only difference being that one contains an effective amount of hydroxylamine and the other does not, a solution containing a hydroxylamine agent leaves substantially higher levels of free Sn″2 ions in solution even after a selected reasonable time interval. As a preferred embodiment,
When enough hydroxylamine is added to stabilize normal autooxidation, the net effect (compared to a similar solution but without hydroxylamine agent) is greater than a bath without hydroxylamine. There is an observed "increase" or maintenance of the measured Sn content of about 30%, preferably 50%, more preferably 70%, over a substantially longer period of time, preferably a typical use solution. For 2-3 weeks - a real effect is achieved as the layer maintains a high concentration of free Sn'' ions. Hydroxylamine sulfate is actually S
It has been observed that it does not increase n''2, but prevents its decrease by minimizing auto-oxidation to Sn''4.

Importantly, it has been discovered that the effective level or amount may be 1, substantially lower than the level of hydroxylamine previously thought to be necessary in plating solutions. That's true. Preferably, the copper-tin coating bath used in the method of the invention contains from about 0.01% to about 0.4% by weight.
% by weight, the layer preferably contains a hydroxylamine agent at a level ranging from about 0.602% to about 0.3% by weight. A similar concentration expressed as weight percent of hydroxylamine per volume of solution used may be used instead.
This is because the working solution is a predominantly aqueous solution with a specific gravity of 1. - layer Preferably, the hydroxylamine agent is from about 0.05% to about 0.2% by weight in the copper-tin coating solution of the present invention.
% level, preferably at a level of about 0.07% to about 0.1%. Again, such levels are substantially lower than those commonly disclosed in the art.

Without wishing to be bound by theory, it is believed that the presence of hydroxylamine in the coating solution used in the method of the present invention increases the stability of the Sn''2 ions in the resulting solution. This property is believed to be due to the reducing ability of the hydroxylamine material over the useful pH range.

An improved bronze colored coating is obtained using a copper:tin weight ratio of about 2.0 to about 0.5. Preferably the copper to tin ratio ranges from about 1.5 to about 1.0, preferably from about 1.3 to about 1.2.

The preferred pH range for baths or use solutions of the invention is from about O to
about 4,-layers, preferably in the range of about 0.2 to about 2.0. The pH of the solution may be adjusted by using copper, tin or other salts or acids.

[M is particularly useful. Such selection is well within the routine of those skilled in the art.

The compositions and methods of the invention may employ aliphatic amines; preferred materials include about 8 to about 16 carbon atoms, -
The layer preferably includes a primary aliphatic amine having from about 10 to about 16 carbon atoms, even more preferably from about 12 to about 16 carbon atoms, with CI4 primary amines being most preferred;
Although not limited to, such materials include:
Levels of about 0.05 to about 0.20% by weight are used. These materials act as wetting agents, helping to stabilize the consistency of the alloy under adverse conditions and providing the desired @:f
It is believed to help maintain the A ratio, ie approximately 80=20.

As indicated above, the aqueous acidic plating baths or use solutions of the present invention have been found to provide excellent plating results even when those plating use solutions or baths contain significant amounts of ferrous iron. are doing. As is recognized in the art, when a ferrous metal surface is initially treated with a ferrous-free bath, the etching action of the bath results in dissolution and concomitant accumulation of ferrous iron during plating. Therefore, the plating baths of the present invention may also contain ferrous ions at levels or amounts up to the saturation point of ferrous ions. The amount or level of ferrous ion in the iron is typically between about 1 and 80, measured as Fe+2.
Even when such typical amounts of ferrous ion are present in the bath, which would be in the range of g/l, and the ferrous ion content is greater than the saturation point of the bath, high quality copper
It has been recognized that tin coatings can be produced1
Although certain particular and/or preferred levels or ranges have been given for the concentrations of the components of the plating solutions of the present invention,
It will be appreciated that these concentrations are merely examples of those that may be used.For example, in some cases it may be satisfactory to use concentrations, levels or ranges of these ingredients outside the indicated ranges. A person skilled in the art will therefore be able to determine the concentration of each of these components to be used in each case, depending on the type of ferrous metal surface to be treated, the desired non-electroplated copper-tin coating, and the concentration of each of these components to be used in each case. It is believed that the specific type and concentration, range or level of other components in the processing solution could be readily determined as well.

The use solutions or baths of the present invention are capable of uniquely improving the color of alloy coatings applied onto metal surfaces. Hydroxylamine reduces the automatic oxidation of free Sn'' ions in solution by about 70% over conventional solutions, thereby lowering bath operating costs and increasing lifetime efficiency.

In the method of the present invention, a ferrous metal surface, such as a long steel wire, is treated with the composition of the present invention by contacting the ferrous metal surface with the improved hydroxylamine-containing steel tinning solution or bath of the present invention. 1. It is preferable to first clean using a suitable cleaning method, which optionally includes pickling with conventional agents such as sulfuric or hydrochloric acid, alkali metal hydroxides and/or cleaners. and some combinations of these cleaning or pretreatment steps. Following cleaning or pretreatment of the steel surface,
Contact with the improved copper-tin plating bath of the present invention. Depending on the particular shape of the iron surface or article being treated, a variety of conventional contact methods can be used, such as dipping, spraying, flushing, etc. When the ferrous surface to be treated is a steel wire, the wire is preferably immersed in the improved steel-tinning bath or the solution used, while the wire is immersed in the steel-tinning bath of the invention. is about 21 to about 55°C, preferably about 26 to about 3
Under these preferred conditions, it is desirable to maintain a temperature in the range of 8° C., where immersion times of about 20 seconds to 5 minutes are typical after removing the improved steel of the present invention from the tinning bath or solution. , the ferrous metal surface may be rinsed with water and dried.

In addition to the preferred embodiments and essential steps specifically mentioned above,
Metal articles or surfaces subjected to the treatment of the present invention may optionally be subjected to one or more of the many commercial or conventional methods to which such articles or surfaces are normally subjected, including, for example, fragmentation. Pre-treatment and post-treatment rinsing may be included to remove or otherwise prepare the surface.

If the ferrous surface to be treated according to the present method is a steel wire, it may be desirable to apply a suitable lubricant to the copper-tin electroless plating to facilitate subsequent drawing operations. Lubricants are known in the art and include many soap and borax-containing compositions, which include copper and
May be applied to tinned wire and then left to dry,
The wire may then be subjected to the desired drawing operation; after such drawing operation, the steel-tin finish of the wire should be very bright and uniform, indicating good adhesion. It's clear. Furthermore, the solution of the present invention can be used for decorative copper-tin coatings as well as
It has been found that it may be used to form copper-tin coatings useful as lubricants for warm forming operations.

The present invention also improves replenishment compositions due to the greater stability of the bath compositions of the present invention (resulting in reduced auto-oxidation of Sn''2). The solution contains a rather high copper=tlJ ratio.The present invention therefore provides a replenishment composition useful for forming aqueous acidic steel-tin coating compositions that coat ferrous metal surfaces without the application of electrical current. copper ions present at a level of from about 10 to about 25% by weight, tin ions present at a level of from about 2 to about 20% by weight, and from about 0.65 to about 5% by weight. Also included are replenishment compositions comprising a hydroxylamine agent present at a level of from about 0.05% to about 0.0%.
Contains 20% by weight fatty acid amines.

To further illustrate the advantages and advantages of the present invention, examples are now provided. It will be understood that the examples are given by way of illustration and are not intended to limit the scope of the invention.

Example 1 2 g/l of 5nSO<and I Ml/IH2S O4
Two solutions were made using 1 y/l of hydroxylamine sulfate was added to one of the solutions. After standing for 10 days, the solutions were analyzed for 5n112. The sample containing hydroxylamine was 64
It contained 0 ppm of Sn″2, while the other contained 19
It contained 0 ppm of Sn″2.

Example 2 To determine the effect of hydroxylamine on the coating quality of Cu/Sn coating solutions, two commercial steel-tin baths were constructed, one containing 1 y/l hydroxylamine sulfate. Pre-cleaned wires were coated with each bath. The color of coatings deposited by baths containing hydroxylamine was improved.

Claims (13)

[Claims] (1) An improved aqueous acidic use solution composition useful for forming copper-tin coatings with improved color on ferrous metal surfaces without the application of electrical current, comprising: (a) from about 0.25 to (b) copper ions in the range of about 0.6% by weight; (b) tin ions in the range of about 0.15 to about 0.6% by weight;
and (c) an effective amount of a hydroxylamine agent. 2. The composition of claim 1, wherein the hydroxylamine agent is present at a level of about 0.01 to about 0.4% by weight. 3. The composition of claim 1 further comprising an aliphatic amine at a level of about 0.05 to about 0.20% by weight. 4. The composition of claim 1, wherein the copper:tin weight ratio ranges from about 2.0 to about 0.5. (5) The composition according to claim 1, wherein the hydroxylamine agent is hydroxylamine or sulfate. (6) Claim 4, wherein the copper:tin ratio is about 1.5 to about 1.0.
The composition described in . 7. The composition of claim 1, wherein copper ions are present at a level of about 0.30 to about 0.45% by weight. (8) Claim 6, wherein the copper:tin ratio is about 1.3 to about 1.2.
The composition described in . 9. The composition of claim 3, wherein the aliphatic amine is a C_8-C_1_6 primary aliphatic amine and is present at a level of about 0.05 to about 0.20% by weight. (10) Treating a ferrous metal surface to be coated with the coating composition of claim 1 and leaving the composition in contact with the ferrous metal surface for a sufficient period of time to cause the formation of a copper-tin coating. A method of forming a copper-tin coating on a ferrous metal surface consisting of maintaining it. (11) Treating a ferrous metal surface to be coated with the coating composition of claim 2 and leaving the composition in contact with the ferrous metal surface for a sufficient period of time to effect the formation of a copper-tin coating. A method of forming a copper-tin coating on a ferrous metal surface consisting of maintaining it. (12) Approximately 1 to 80 g/l measured as Fe^+^2
2. The composition of claim 1, containing a level of ferrous ion. (13) In a replenishment composition useful for forming an aqueous acidic copper-tin coating composition that is a coating composition useful for forming a copper-tin coating on a ferrous metal surface without the application of an electric current, the composition comprises: 1
A supplement comprising copper ions present at a level of 0 to about 25% by weight, tin ions present at a level of about 2 to about 20% by weight, and a hydroxylamine agent present at a level of about 0.5 to about 5% by weight. Composition.