JPS62270791A - Stabilizer of stannic ion - Google Patents

Abstract

In acid Sn(II)-containing electrolytes for staining anodically produced oxide layers on aluminium or aluminium alloys or for electroplating, the Sn(II) becomes oxidised. Adding substances to the electrolyte, so called stabilisers, may prevent the oxidation to a greater or lesser degree, i.e. Sn(II) can be stabilised to a greater or lesser degree. The effectiveness of the stabiliser furthermore governs the quality of the deposits or the coloration of the anodised layer. The quality of the surface treatment is known to deteriorate in the presence of Sn(IV) in substantial amounts alongside Sn(II) as a consequence of inadequate stabilisation of the Sn(II). An acid Sn(II)-containing electrolyte with a soluble diphenylamine or substituted diphenylamine derivative added stabilises the Sn(II) and yields faultless colorations.

Description

DETAILED DESCRIPTION OF THE INVENTION 3. Detailed Description of the Invention The present invention comprises acidic divalent tin used for coloring or electroplating an oxide layer on anodized aluminum or aluminum alloys. Concerning electrolyte stabilization.

Divalent tin salts are used, for example in the form of acidic sulphate, fluorobalate or chloride solutions, for coloring or electroplating anodic oxide layers on aluminum or aluminum alloys.

★Only acidic sulfate baths are known to contain simple divalent tin ions. In all other electrolytes, tin is at least partially bound in complex form.

One difficulty encountered when coloring or electroplating anodic oxide films on aluminum or its alloys in acidic solutions is that divalent tin ions are oxidized to tetravalent tin ions during the reaction. be. By adding a substance called a stabilizer to the electrolyte, this oxidation can be prevented to some extent, that is, the divalent tin ions can be stabilized to some extent.

The effect of the stabilizer is decisive for the quality of the plating deposit or the color development of the anodic oxide layer. As is generally known,
When ions with different valences, ie, divalent tin and tetravalent tin, are present in large quantities, it is difficult to stabilize the divalent tin, and the quality of the surface treatment deteriorates. It is therefore necessary to try to keep the soot as divalent tin ions in acidic solutions.

Aromatic compounds containing amino groups, such as aminophenol and dimethylaniline, are known as stabilizers for acidic electrolytes.

Although these compounds have a stabilizing effect on divalent tin ions, they cannot prevent the divalent tin ions from being partially oxidized to tetravalent ions. Therefore, the coloring quality of anodic oxides, especially on aluminum or its alloys, is affected thereby. If the divalent tin ions are not properly stabilized, the color depth and color uniformity of the dark colored ions is often insufficient. This point is a significant drawback of the stabilizers used up to now. The ideal stabilizer would be one that completely stabilizes divalent tin ions. However, when actually using the above additives to color an anode coating on aluminum or its alloy, it is difficult to develop a dark color such as dark bronze or black. Furthermore, since the diffusion effect of the electrolyte is not sufficient, the coloring is shaded in the peripheral region. The coloring process progresses and after about 10 minutes, excessive coloring occurs and a gold layer deposits on the surface. The resulting colored surfaces are associated with corrosion and bath contamination problems when cleaned.

The present invention has discovered that diphenylamine or substituted diphenylamine derivatives substantially stabilize divalent tin ions in acidic solutions. These compounds also improve the diffusivity of divalent tin-containing electrolytes, resulting in better current distribution.

Accordingly, the present invention provides compositions for stabilizing divalent tin ions comprising diphenylamine or substituted diphenylamine derivatives or mixtures thereof as active ingredients soluble in acidic media.

Advantageously, at least 5 mg of the diphenylamine according to the invention is dissolved in water 11 at a temperature of 20° C. and a pH of less than 5.

Particularly suitable diphenylamines of the present invention have the general formula (1) where the substituents R, -R, are each independently hydrogen; at most one halogen in each ring; at most one nitro in each ring; groups; at most 2 -COOM in each ring; at most 2 -SO3M in each ring; at most 2 -NHx in each ring
a C1-C4 alkyl group, or at most one phenylamino group in each ring, and the substituent R11 is hydrogen; a C1-C4 alkyl group; β-
ω-Hydroxy = 01 to C4 alkyl group; phenyl group; or →B-OhR+z, where B is each independently -c, +t, -, -CjH&-.

or -〇4HII-, n is 1 to 20, and R
1! is H, -SO3M, or -CHtCOOM, where M is hydrogen or an equivalent cation), or a mixture of these compounds.

Halogen can be fluorine, chlorine or bromine, with chlorine being preferred. M can be an equivalent cation, an alkyl metal, an equivalent alkaline earth metal or a substituted ammonium, with hydrogen being preferred.

→B-OhRI! In each residue, B is 10ZH
4- or -CH(CH3)C41g- is preferred, but Ctl(-1 is more preferred. n is preferably 1 to 5, and R1, is preferably -5O3p).

Each ring independently represents 01 to C4 alkyl group 1.2
Or it is preferable to have three pieces.

Preferred compounds of formula 1 include a total of 1 or 2 7mino groups, a total of 1 or 2 1000M%, or a total of 1 or 2 -SO3M,
or the amino group is -COOM% or -SO3M
The group in combination with the above group is substituted with a phenyl group.

The following substances have been found to be particularly advantageous additives for the compounds of the invention:

2-Amino-diphenylamine-4-amino-diphenylamine 4-amino-diphenylamine-2-carboxylic acid diphenylamine-4-sulfonic acid 2-amino-diphenylamine-4-sulfonic acid 4-amino-diphenylamine-2-sulfonic acid 4.4' -Diamino-diphenylamine-2-sulfonic acid 4'-amino-4-nitrodiphenylamine-2-sulfonic acid 1-amino-2,4-di(phenylamino)benzene-
5-sulfonic acid, or diphenylamine-4,4'-disulfonic acid, or a mixture thereof.

A preferred mixture is a diphenylamine-disulfonic acid mixture based on diphenylamine-monosulfonic acid.

Compounds of formula 1 can be prepared by known methods.

Preferably, the stabilizer composition further contains an organic or inorganic acid as an auxiliary agent to adjust the pH, and further contains a solubilizing agent and/or a sequestering agent.
Less than is preferred. The concentration of stabilizer can vary up to 95% by weight.

In a preferred embodiment of the invention, the composition comprises a divalent tin-containing electrolyte with the addition of any of the above-mentioned auxiliaries in addition to the stabilizer.

Suitable divalent tin-containing electrolytes are divalent tin salts used for surface treatment, in particular for the purpose of coloring or electroplating oxide layers formed by anodization on aluminum or aluminum alloys.

Preferred divalent tin-containing electrolytes are, for example, acidic divalent tin sulfates, fluorobalates or chlorides, with divalent tin sulfates being particularly preferred.

The concentrations of divalent tin-containing electrolyte and stabilizer can vary over a wide range. S thick compositions can be diluted. Advantageously, the stabilizer is in a concentration necessary to effectively stabilize the divalent tin ions present in the composition.

Further, the stabilizer may be used in excess.

Advantageously, compositions comprising the stabilizer and divalent tin-containing electrolyte of the present invention are acidic in pt+. pH is 1-5
is preferred, but it is more preferred that it be as low as about 1. It is preferable to adjust the pH of the composition with sulfuric acid.

The present invention also provides a method of contacting an acidic divalent tin-containing electrolyte with an effective amount of diphenylamine or substituted diphenylamine derivatives or mixtures thereof to prevent oxidation and stabilize divalent tin ions.

Acidic divalent tin-containing electrolyte baths stabilized with diphenylamine as described above, particularly baths necessary for coloring or electroplating oxide layers on anodized aluminum or aluminum alloys, are also part of the invention. form a section. The present invention further provides for the formation of oxide layers on anodized aluminum or aluminum alloys using divalent tin-containing electrolytes stabilized with diphenylamine or substituted diphenylamine derivatives or derivatives thereof. Provides a method for coloring or electroplating.

The divalent tin-containing electrolytes stabilized according to the invention are used to develop color in oxide layers on anodized aluminum or aluminum alloys, and also.

This can be done by known methods, especially for electroplating metal surfaces.

The amount of the stabilizer of the present invention used in the divalent tin-containing electrolyte treatment bath is preferably 20s+g to 1g/l, and more preferably 20s+g to 1g/l.
+*g/j! 〜SO0mg/Jt is preferable, especially 1
00a+g/j! ~200 mg/J is preferred.

The stabilizer may be added to the treatment bath together with the divalent tin-containing electrolyte or separately.

In the composition and treatment bath of the present invention, the weight ratio of divalent tin-containing electrolyte to stabilizer is preferably 2-30:0.02-1.

Surprisingly, by adding some compounds of the present invention to the electrolyte bath, the problem of overcoloring that occurs at an advanced stage of the coloring process does not occur in the coloring of the aluminum oxide layer obtained by anodization. There was found. In the presence of the conventional stabilizers mentioned at the outset, color non-uniformity and darkness are common in colored oxide coatings, but with the use of the stabilizers of the invention By doing so, this problem can be substantially reduced or completely eliminated. This excellent color development is applicable not only to bright tones, but also to dark tones, which have been extremely difficult to achieve to date, especially with regard to color inhomogeneity and depth of tone.

What is particularly surprising is that these compounds are highly effective even in small amounts. A substantial stabilizing effect can be achieved even at a concentration of 20 ppm.

In all respects, the disadvantages of the known stabilizers of acidic divalent tin-containing electrolytes used for color development of aluminum oxide layers obtained by anodization or for electroplating purposes, as described at the outset, are overcome by the present invention. It has been found that the electrolyte does not occur or can be ignored because it is reduced to such an extent that it does not interfere with the above purpose.

To fully appreciate the superiority of the stabilized electrolyte of the present invention over electrolytes used to date,
All factors, ie, stabilization of divalent tin ions, diffusion characteristics/current distribution, and coloring effects, must be considered together.

The following two series of experiments and color development tests were carried out to demonstrate the excellent effect of the stabilization according to the invention and the resulting good color development obtained with aluminum or aluminum alloys anodized in acidic solutions.

The purpose of this series of experiments is to demonstrate the stabilizing effect of the additive according to the invention by means of a rapid test involving treatment with pure oxygen.

An aqueous solution containing 10 g/A' of sulfuric acid and 20 g/l of divalent tin sulfate was prepared. In this condition, tin initially exists as divalent tin. The electrolytic solution 11 was divided into seven containers having the same shape and dimensions.

1st bath: No stabilizer.

Stabilizers were added to other containers.

2nd bath: Paraphenolsulfonic acid, which has been used until now, 20g/II. 3rd bath: N,N-dimethylaniline, a known additive, 100mg/J! 4th bath Nidiphenylamine, 100mg/l 5th bath Nidiphenylamine-4-sulfonic acid, 100w+g7'2 6th bath: 2-Amino-diphenylamine-4-sulfonic acid, 100mg/j! Bath 7: 4-amino-diphenylamine-2-carboxylic acid, 100mg/j! All baths had a pI of 1 and were kept stirred by a magnetic stirrer at room temperature.
Pure oxygen was bubbled at a flow rate of 00 d, and the content of divalent tin ions was analyzed every 30 minutes. The results are shown in FIG.

The same base solution as in experimental series 1 was prepared, and the same containers used in the previous experimental series were filled with electrolyte 11, and all baths had a pH of 1 and were kept at room temperature. Stirring was continued with a magnetic stirrer.

The eighth bath, corresponding to the first bath of the previous experimental series, contained no additives. The next three baths all contained varying concentrations of diphenylamine-4-sulfonic acid.

9th bath: 20mg/l 10th bath: 100mg/j! 11th bath: 20g/Il The 10th bath corresponds to the 5th bath of the previous experimental series.

As in the first series of experiments, each bath was bubbled with pure oxygen through a glass tube at a flow rate of 20 M/min.
The divalent tin ion content was measured every 30 minutes. The results are shown in Figure 2.

As is clear from FIGS. 1 and 2, when no additive was added, most of the divalent tin was converted to tetravalent tin ions in a relatively short period of time. Furthermore, the stabilizing effect is found to vary depending on the added substance and its amount. Although the known additives paraphenolsulfonic acid and N,N-dimethylaniline are added in large amounts, they have a significantly lower effect of stabilizing divalent tin ions than the additive of the present invention. few.

The following examples are not intended to limit the scope of the invention.

〔Example〕

Medium hardness PERALUMAN-100 no 200 X300
X 1.5 mm (7) plates were anodized by the conventional DC/sulfuric acid method.

The thickness of the oxide layer was 20μ. 6ol of these temporary
The sample was placed in the container and treated at a voltage of 15 V for 8 minutes.

These plates were treated for 1 to 12 minutes in baths 1 to 11 of the composition used in experimental series 1 and 2 above.

When the stabilizer of the present invention was used, a completely uniform bronze color was developed without bleaching at all edges. The additives commonly used up to now often produce fringe effects in bronze tones. This is due to the poor diffusion properties of the electrolyte. This shows that the diffusion behavior of divalent tin-containing electrolytes is now better with the novel stabilizers of the invention than with the electrolytes that have been used to date for diffusion purposes.

1 is a graph showing the effect of stabilizers.

1.8...No additive, 2.3...Conventional example, 4 to 7
and 9-11... Examples.

Claims (1)

Claims: 1. A composition for stabilizing divalent tin ions, comprising diphenylamine or a substituted diphenylamine derivative or a mixture thereof as an acidic solvent-soluble active ingredient. 2. The active ingredient has a general formula I ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ I (In the formula, substituents R_1 to R_1_0 are each independently hydrogen; at most one halogen in each ring; one nitro group in each ring; at most two -COOMs in each ring;
At most 2 -SO_3M in each ring; at most 2 in each ring
-NH_2 represents a C1-C4 alkyl group, or at most one phenylamino group in each ring, and the substituent R_1_1 is hydrogen; a C1-C4 alkyl group;
β~ω-Hydroxy-C1-C4 alkyl group; phenyl group;
H_6- or -C_4H_8-, and n is 1 to 2
0 and R_1_2 is H, -SO_3M or -CH
_2COOM, where M is hydrogen or an equivalent cation), or a mixture of these compounds. 3. The active ingredient is 2-amino-diphenylamine-4-amino-diphenylamine-2-amino-diphenylamine-2-carboxylic acid diphenylamine-4-sulfonic acid 2-amino-diphenylamine-4-sulfonic acid 4-amino-diphenylamine-2- Sulfonic acid 4,4'-diamino-diphenylamine-2-sulfonic acid 4'-amino-4-nitrodiphenylamine-2-sulfonic acid 1-amino-2,4-di(phenylamino)benzene-
The composition according to claim 1 or 2, which is 5-sulfonic acid, diphenylamine-4,4'-disulfonic acid, or a mixture thereof. 4. The composition according to claim 3, wherein the active ingredient is a mixture of diphenylamine-monosulfonic acid and diphenylamine-disulfonic acid. 5. The composition according to any one of claims 1 to 4, further comprising a divalent tin-containing electrolyte. 6. The composition according to claim 5, wherein the divalent tin-containing electrolyte is tin sulfate. 7. The composition according to claim 5 or 6, which has an acidic pH. 8. The composition according to claim 6 or 7, which contains sulfuric acid. 9. The weight ratio of divalent tin-containing electrolyte to active ingredient is 2 to 30.
: 0.02 to 1, the composition according to any one of claims 5 to 8. 10. Acidic divalent tin-containing electrolyte baths containing diphenylamine or substituted diphenylamine derivatives or mixtures thereof as active ingredients soluble in acidic solvents. 11. Weight ratio of divalent tin-containing electrolyte to diphenylamine or diphenylamine derivative is 2-30:0.02-
1. The electrolyte bath according to claim 10, which is 12. Stabilizing the acidic divalent tin-containing electrolyte by contacting the acidic divalent tin-containing electrolyte with an effective amount of soluble diphenylamine or a substituted diphenylamine derivative or a mixture thereof to prevent oxidation of divalent tin ions. how to. 13. A method for coloring or electroplating an oxide layer on anodized aluminum or aluminum alloy using a divalent tin-containing electrolyte, the method comprising using a divalent tin-containing electrolyte as a soluble diphenylamine or Stabilization with substituted diphenylamine derivatives or mixtures thereof. 14. The method according to claim 12, wherein 20 mg to 1 g of diphenylamine or a diphenylamine derivative is used per 1 liter of divalent tin-containing electrolyte bath. 15. The method according to claim 13, wherein 20 mg to 1 g of diphenylamine or a diphenylamine derivative is used per 1 liter of divalent tin-containing electrolyte bath.