A WATER-BASED COMPOSITION FOR POST-TREATMENT OF METAL SURFACES

Abstract

A water-based composition for post-treatment of metal surfaces, preferably a silver or silver alloy surface, including: an alkanethiol an anionic, cationic, non-ionic, amphoteric or zwitterionic surfactant with a HLB value of 12 to 18, a compound of the general formula I:

##STR00001##

wherein R.sub.1 is H, CH.sub.3, C.sub.2H.sub.5, (C.sub.2H.sub.4O).sub.pH, (C.sub.2H.sub.4O).sub.pCH.sub.3, (C.sub.2H.sub.4O).sub.pCH(CH.sub.3).sub.2, (C.sub.2H.sub.4).sub.pC(CH.sub.3).sub.3, wherein p is 1 to 20, R.sub.2 is H, or CH.sub.3 n is an integer in the range of 0 to 3, m is an integer in the range of 0 to 2.

Claims

1. A water-based composition for post-treatment of metal surfaces, comprising an alkanethiol, an anionic, cationic, non-ionic, amphoteric or zwitterionic surfactant with a HLB value of 12 to 18, characterized in that the water-based composition further contains a compound of the general formula I: ##STR00004## wherein R.sub.1 is H, CH.sub.3, C2H.sub.5, (C.sub.2H.sub.4O).sub.pH, (C.sub.2H.sub.4O).sub.pCH.sub.3, -(C.sub.2H.sub.4O).sub.pCH(CH.sub.3).sub.2, (C.sub.2H.sub.4O).sub.pC(CH.sub.3).sub.3, wherein p is an integer in the range of 1 to 20, R2 is H or CH.sub.3, n is an integer in the range of 0 to 3, m is an integer in the range of 0, 1 or 2.

2. The water-based composition according to claim 1, wherein in the compound of formula I is m=0, n in the range of 0 to 3 and R1 is independently selected from the group consisting of H, CH.sub.3, C.sub.2H.sub.5 and (C.sub.2H.sub.4O).sub.pH wherein p in the range 2 to 6.

3. The water-based composition according to claim 1, wherein the compound of formula I is selected from the group consisting of 2,3,6,7-tetramethyl-4-octyne-3,6-diol, 2,5,8,11-tetramethyl-6-dodecyn-5,8-diol ethoxylate, 2,4,7,9-tetramethyl-5-decyne-4,7-diol ethoxylate, 2,4,7,9-tetramethyl-5-decyne-4,7-diol-bispolyoxyethyleneether, and 2,4,7,9-tetramethyl-5-decyne-4,7-diol.

4. The water-based composition according to claim 1, wherein the surfactant is an ethoxylated or propoxylated alkyl, ethoxylated or propoxylated amine, ethoxylated or propoxylated amide, ethoxylated or propoxylated alcohol, or a mixture thereof.

5. The water-based composition according to claim 1, wherein the surfactant has the general formula II
R.sub.3O(CH.sub.2CH.sub.2O).sub.xH (II) wherein R.sub.3 is a linear or branched alkyl group, having 6-15 carbon atoms, x is an integer in the range of 3-15.

6. The water-based composition according to claim 1, wherein the alkanethiol is a C.sub.10- to C.sub.20-alkanethiol.

7. The water-based composition according to claim 1, wherein the composition comprises a co-emulsifier.

8. The water-based composition according to claim 7, wherein the co-emulsifier has the general formula III
R.sub.4O(CH.sub.2CH.sub.2O).sub.yH (III) wherein R4 is a linear or branched alkyl group, having 16-20 carbon atoms, y is an integer in the range of 2-10.

9. The water-based composition according to claim 7, wherein the co-emulsifier is a polyalkylene glycol ether.

10. The water-based composition according to claim 1, wherein the composition is free of chromate and/or free of organic solvent.

11. The water-based composition according to claim 1, having wherein the composition has a pH in the range of 1 to 10.

12. (canceled)

13. A method for post-treatment of a metal surface, in this order, the steps a. providing a metal surface, b. contacting the metal surface, with a water-based composition according to claim 1.

14. The method according to claim 13, wherein the contacting in step b. is applied by immersing, by spraying, or by any other suitable method, or combination of any of the foregoing, allowing the contact between the metal and the water-based composition.

15. The method according to claim 13, wherein the contacting in step b. takes place under applying an electrical current between the metal surface, and at least one electrode when the metal is immersed into the claim solution.

16. The water-based composition according to claim 1, wherein the metal surface is a silver or silver alloy surface.

Description

EXAMPLES

[0040] Hereinafter, the invention is illustrated by working examples.

Inventive Example 1

[0041] Water-based compositions were provided, wherein the concentrations of c.) compound of the general formula I (compound c1)), vary while the concentrations of other components are fixed, respectively.

[0042] The water-based composition was made by dissolving the following components in water: [0043] a. alkanethiol: octadecanethiol. (CAS Nr. 2885-00-9) amount: 2.5 g/L [0044] b. surfactant: PEG-11 C10-11 Oxo alcohol ethoxylates (CAS Nr: 78330-20-8) amount: 17.5 g/l [0045] c. compound of the general formula I: c1) 2,5,8,11-Tetramethyl-6-dodecyn-5,8-diol ethoxylate, (CAS Nr. 169117-72-0) in an amount: 2, 3 or 4 g/l [0046] d. co-emulsifier: Alcohol C16-18 polyalkylene glycol ether, (CAS Nr. 68002-96-0) amount: 2,5 g/L.

Inventive Example 2

[0047] Water-based composition was provided wherein the following compound c2) 2,4,7,9-tetramethyl-5-decyne-4,7-diol ethoxylate (CAS Nr. 9014-85-1) and c3) 2,4,7, 9-tetramethyl-5-decyne-4,7-diol (CAS Nr. 126-86-3) of c.) compound of the general formula I were separately used at same concentrations:

[0048] The water-based composition was made by dissolving the following components in water: [0049] a. alkanethiol: octadecanethiol. (CAS Nr. 2885-00-9) amount: 2.5 g/L [0050] b. surfactant: PEG-11 C10-11 Oxo alcohol ethoxylates (CAS Nr: 78330-20-8) amount: 17.5 g/l [0051] c. compound of the general formula I (c2 or c3): amount: 2 g/l [0052] d. co-emulsifier: Alcohol C16-18 polyalkylene glycol ether, (CAS Nr. 68002-96-0) amount: 2.5 g/L.

Comparative Example

[0053] Comparative water-based compositions were provided, comprising a., b. and d. wherein the concentrations of compound of the general formula I (c1-c3) was zero and the other concentrations were as stated above.

1. Methods

[0054] The post-treatment was performed on silver plated copper panels. These panels, having a copper surface, may be provided from the following steps: [0055] Providing Copper Panels [0056] 1. Degrease Uniclean 260 (electrophoretic alkaline cleaner) cathodic 7V/45 C./30 sec [0057] 2. Activate: Uniclean 675 (mild acidic activator)immersion/RT/30 sec [0058] 3. Pre-silver Pre-silver (low silver concentrated solution) cathodic 3V/RT/15 sec [0059] 4. Silver Silverlume Plus (bright silver deposition solution) cathodic 1 ASD/RT/5 min [0060] or AgO-56 (technical silver deposition solution) cathodic 1 ASD/RT/5 min [0061] or Argalux NC mod. (cyanide-free bright silver deposition solution) cathodic 0.8 ASD/RT/5 min
wherein RT is room temperature between 222 C.; DI water is deionized water; ASD is Ampere per square decimeter A/dm.sup.2 and V is volt/voltage.

[0062] In the sense of this invention the post-treatment composition may work also with otherwise obtained silver plated surfaces in the field of use of technical or decorative (with or without cyanide) silver deposition solutions for silver plating to avoid tarnishing after this silver plating.

[0063] The inventive water-based compositions according to the invention for post-treatment and the comparative water-based compositions were used under various conditions (see tests below).

[0064] After post-treatment in the water-based composition all samples were rinsed with: [0065] Hot DI water rinse, [0066] Cold DI water rinse and [0067] dried with compressed air. [0068] Optical evaluation after post-treatment with the inventive and comparative composition and subsequent sulphide test due to: [0069] Residues immediately after post-treatment and rinse [0070] Colorations and tarnishing after sulphide test

[0071] The observations have been carried out without any instruments by skilled person. [0072] Sulphide test [0073] Material: Glass beaker [0074] Chemicals: Potassium Sulphide 44% K.sub.2S, 2% w/w in water [0075] Temperature: 22 2 C. [0076] Dipping time: 5-10 min [0077] Evaluation by the skilled person [0078] according to colour intensity

2. Results

2.1 Rinsing Capability Test

[0079] The inventive water-based compositions showed improved rinsing capability in comparison with the comparative water-based compositions and eliminate oily residues issues completely. The treatment of Silverlume Plus, AgO-56 and Argalux NC mod. plated silver surfaces with the comparative water-based compositions the surfaces showed poor rinsing capability, whereas the inventive water-based compositions show very good rinsing capability.

2.2 Anti Tarnishing Tests

[0080] The inventive water-based compositions showed improved anti-tarnish protection in comparison with the comparative water-based compositions without the compound of the general formula I (c1-c3). The not-treated silver surfaces obtained from silver plating solutions as Silverlume Plus, AgO-56 and Argalux NC mod. exhibit very poor anti-tarnish protection. These plated silver surfaces treated with the comparative water-based compositions showed less discoloration after sulphide test, whereas the surfaces treated with the inventive water-based compositions show few to no discoloration.

[0081] Test material: bright silver plated surface (Silverlume Plus)

[0082] Water-based composition conditions: pH 2.5Temperature 55 C.agitation 200 RPMimmersion process for 1 min, rinse & dry.

TABLE-US-00001 Test material: bright decorative silver layer (Silverlume Plus) Compound of 0 g/L 2 g/L 3 g/L 4 g/L formula I (comparative (c1-c3) (c1) (c1) example) Residues Very poor Excellent Excellent Excellent (many (none) (none) (none) residues) Anti-tarnish Very poor Improved Strongly Excellent (after 5 min into (dark (yellow improved (no discoloration) K.sub.2S 2%) discoloration) discoloration) (Yellow to no discoloration)

[0083] Test material: bright silver plated surface (Argalux NC mod), cyanide free

[0084] Water-based composition conditions: pH 2.5Temperature 55 C.Agitation 200 RPM1 min immersion process, rinse & dry.

TABLE-US-00002 Test material: bright silver cyanide free (Argalux NC mod.) Compound (c1) 0 g/L 3 g/L 4 g/L of formula I (comparative example) Residues Poor (many) Excellent (none) Excellent (none) Anti-tarnish Very poor Strongly improved Excellent (no (after 5 min (dark colored) (yellow colored) discoloration) into K.sub.2S 2%)

[0085] Test material: technical silver plated surface (AgO-56)

[0086] Water-based composition conditions: pH 2.5Temperature 55 C.agitation 200 RPMimmersion process for 1 min, rinse & dry.

TABLE-US-00003 Test material: technical silver (AgO-56) Compound (c1) 0 g/L 3 g/L 4 g/L of formula I (comparative example) Residues Poor (many) Excellent (none) Excellent (none) Anti-tarnish Very poor Strongly improved Excellent (no (after 5 min (dark colored) (yellow to no discoloration) into K.sub.2S 2%) discoloration)

2.3 Cathodic Use

[0087] Test material: technical silver plated surface (AgO-56)

[0088] Water-based composition conditions: pH 2.5Temperature 55 C.Agitation 200 RPMimmersion for 1 min or cathodic 0.5 A/dm.sup.2 for 1 min, rinse & dry

TABLE-US-00004 Test material: technical silver (AgO-56) Compound 0 g/L 3 g/L (c1) of (comparative example) formula I Process Immersion Cathodic Immersion Cathodic Residues Poor (many) Poor (many) Excellent (none) Excellent (none) Anti-tarnish 5 min 10 min 5 min 10 min (dipping time Very poor Strongly Good (yellow to no Excellent (no into K.sub.2S 2%) (dark colored) improved discoloration) discoloration)

3. Conclusions

[0089] The inventive water-based compositions do improve: [0090] The wettability of immersed metal surfaces, especially silver. [0091] The formation of a self-assembled thiol monolayer onto immersed silver surfaces, making a non-polar film and enhancing anti-tarnish properties. [0092] The rinsing of hydrophobic alkanethiol rests after silver surfaces treatment with water based solution of the invention. [0093] Immersion and electrophoretic uses are suitable in avoiding tarnishing of the metal plated surfaces after metal plating.