WO2010060358A1

WO2010060358A1 - Sealing reagent for aluminum alloy

Info

Publication number: WO2010060358A1
Application number: PCT/CN2009/074962
Authority: WO
Inventors: Ping Lu; Chunnan Gao; Xiaolu Cui
Original assignee: BYD Co Ltd
Current assignee: BYD Co Ltd
Priority date: 2008-11-27
Filing date: 2009-11-16
Publication date: 2010-06-03
Anticipated expiration: 2011-05-27
Also published as: US20100129560A1; EP2350356B1; EP2350356A1; CN101736386A; CN101736386B; EP2350356A4; US8449667B2

Abstract

A nickel-free sealing reagent is disclosed, which comprises an alkyl sodium sulfonate compound, a dispersing agent, and a siloxane defoaming agent. And a method of sealing an alloy is disclosed too, which comprises applying a nickel-free sealing reagent to the alloy. The sealing agent comprises an alkyl sodium sulfonate compound; a dispersing agent; and a siloxane defoaming agent.

Description

SEALING REAGENT FOR ALUMINUM ALLOY

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority to Chinese Patent Application No. 200810217696.8, filed November 27, 2008, the entirety of which is hereby incorporated by reference.

FIELD

The present invention relates to sealing technology of aluminum alloy, and more particularly to a nickel-free sealing reagent for aluminum alloy anodizing.

BACKGROUND

At present, moderate- or low-temperature sealing reagents are widely used to reduce the porosity and adsorption capacity of anodic oxide films in the processing after aluminum alloy anodizing. Such reagents are convenient to use, and many of them contain nickel ions. Because of nickel allergy caused by frequent contact of nickel containing metal ornamentals with human body, there are standards in many countries that limit the use of nickel-containing ornamentals, such as BS EN 1811 :1999 and BS EN 12472:2005. Therefore, nickel-free sealing reagents for aluminum alloy anodizing are urgently needed.

In prior art, a relatively mature nickel-free sealing reagent is fluotitanate moderate temperature sealing reagents, which includes 5-10 g/L potassium fluotitanate, 0.05-0.15 g/L cyclohexanone and 0.05-0.15 g/L isoamyl alcohol. It is used at the temperature of 55-65 ⁰C with treatment time of 1.0-1.5 μm/min. This sealing reagent is nickel-free, but some dyed workpieces lose weight significantly after being processed by this sealing reagent.

SUMMARY In viewing thereof, the present invention is directed to solve at least one of the problems existing in the prior art. Accordingly, a nickel-free sealing reagent is disclosed, which comprises an alkyl sodium sulfonate compound, a dispersing agent, and a siloxane defoaming agent. In one embodiment, the nickel-free sealing reagent further comprises a buffering agent.

Another embodiment discloses a method of sealing an alloy which comprising applying a nickel-free sealing reagent to the alloy, wherein the sealing agent comprising an alkyl sodium sulfonate compound; a dispersing agent; and a siloxane defoaming agent.

DETAILED DESCRIPTION

It will be appreciated by those of ordinary skill in the art that the embodiments disclosed herein can be embodied in other specific forms without departing from the spirit or essential character thereof. The presently disclosed embodiments are therefore considered in all respects to be illustrative and not restrictive.

According to one embodiment, a sealing reagent for aluminum alloy is an aqueous solution comprising an alkyl sodium sulfonate compound, a dispersing agent, a siloxane defoaming agent. According to another embodiment, the sealing reagent may further comprise a buffering agent.

The alkyl sodium sulfonate compound is a nickel-free salt of the sealing reagent. The term "nickel-free" means substantially free of nickel or nickel-containing compounds. In some embodiments, the alkyl sodium sulfonate compound comprises one or more of sodium dodecyl sulfonate, sodium dodecyl benzene sulfonate, sodium cetyl sulfonate, and sodium cetyl benzene sulfonate.

The dispersing agent can be any dispersing agent known by one skilled in the art. In some embodiments, the dispersing agent comprises one or more of sodium naphthylmethylene sulfonate, benzyl naphthalenesulfonate/formaldehyde condensation polymer (namely dispersing agent CNF), and methyl naphthalenesulfonate /formaldehyde condensation polymer.

The defoaming agent can reduce the large amount of foam formed when the sealing reagent is stirred. Siloxane defoaming agents are used in some embodiments. The siloxane defoaming agent comprises one or more of polydimethylsiloxane, polyether modified polysiloxane, ethoxyl modified trisiloxane, and siloxane-oxyalkylene copolymers.

One effect of the defoaming agent is replacing any foam stabilizer on the liquid-air interface. The defoaming agent must have a higher surface activity than the foam stabilizer so as to enter the foam and spread spontaneously, which repulse the stable surfactant and stop the self-repairing of the liquid membrane. High surface viscosity could stabilize the foam, so the defoaming agent must have a low surface viscosity. The siloxane defoaming agent is a good defoaming agent because Si-O chain is a non-polar highly hydrophobic molecule. Siloxane has a lower surface energy than carbon chain hydrocarbons, as well as a lower surface tension than common surfactants. At the same time, it has a very low surface viscosity, and the influences of its chemical inertia on environment and human are very little too.

The buffering agent has the function of stabilizing the pH of the sealing system for a long period of time. In some embodiments, the buffering agent comprises one or more of sodium acetate, disodium hydrogen phosphate, sodium dihydrogen phosphate, and sodium citrate.

According to one embodiment, the alkyl sodium sulfonate compound accounts for about 3 weight percent to about 10 weight percent of the sealing reagent. The dispersing agent accounts for about 1 weight percent to about 2 weight percent of the sealing reagent. The siloxane defoaming agent accounts for about 1 weight percent to about 2 weight percent of the sealing reagent. The buffering agent accounts for about 1 weight percent to about 5 weight percent of the sealing reagent. The pH of the sealing reagent provided by the present invention for aluminum alloy is not limited to any specific value. In some embodiments, the sealing reagent may have pH from about 5 to about 6.5.

The sealing reagent of the present disclosure can be used for sealing processes after anodizing for various aluminum alloys. The aluminum alloys can be any of Series lxxx to 7xxx aluminum alloys or superhard aluminium alloys. Series lxxx aluminum alloys are high purity aluminum (> about 99. 99 wt %); Series 2xxx aluminum alloys contain main alloy element Cu, and other elements such as Mn, Mg, Pb and Bi; Series 3xxx aluminum alloys contain main alloy element Mn; Series 4xxx aluminum alloys contain main alloy element Si; Series 5xxx aluminum alloys contain main alloy element Mg; Series 6xxx aluminum alloys contain main alloy element Mg and Si; Series 7xxx aluminum alloys contain main alloy element Zn, and other elements such as Mg and Cu. The hardness of the superhard aluminium alloys, which contain main alloy element Zn, Pb, Mg and Cu, is similar to that of steel. The alloys above may further contain a small amount other elements such as Ni and Fe.

The technology of aluminum alloy anodizing can be any technology known by one skilled in the art. In some embodiments, the process of aluminum alloy anodizing includes the steps of: taking the aluminum alloy into an electrolytic bath containing sulfuric acid solution with a concentration of about 180-220 g/L; anodizing for about 30-50 minutes using the aluminum alloy as an anode, with the voltage of about 12-18 V, the current density of about 1-2 A/dm², and the temperature of about 19-22 ^°C ; taking the aluminum alloy out when the anodizing is completed and cleaning the aluminum alloy. The aluminum alloy further can be pre-treated before anodizing. The pretreatment may include the steps of: placing the aluminum alloy into a 30-40 g/L degreasing solution at about 50-60 ⁰C for about 3-5 minutes; removing the grease on the aluminum alloy surface to obtain a substantially oil-free substrate; placing the substrate into a mixed acid solution of about 500-700 g/L phosphoric acid and about 150-200 g/L sulphuric acid for chemical polishing for about 3-10 seconds, and then immediately transferring the substrate into water to wash out the acid on the substrate surface; placing the substrate into a 10-40 g/L sodium hydroxide solution for about 1-3 minutes, and then immediately transferring the substrate into water to wash out the alkali on the substrate surface.

The following are various embodiments of nickel-free reagent in sealing process according to the present disclosure.

EXAMPLE 1 (1) Anodizing of 1050 aluminum alloy

A 1050 aluminum alloy as a substrate is placed into a 35 g/L degreasing solution at about 60 ⁰C for about 5 minutes to wash out the grease on the alloy surface. Then the substrate is placed into a mixed acid solution of about 600 g/L phosphoric acid and about 200 g/L sulphuric acid for about 10 seconds for chemical polishing, after which step the substrate is immediately transferred into water to wash out the acid remaining on the substrate surface. The substrate is then placed into a 30 g/L sodium hydroxide solution for about 3 minutes, which is then immediately transferred into water to wash out the alkali on the substrate surface. The above aluminum alloy substrate is placed into an electrolytic bath containing sulfuric acid solution with a concentration of about 220 g/L, which is anodized as an anode for about 50 minutes. The anodizing condition includes the voltage of about 18 V, the current density of about 2 A/dm², and the temperature of about 20 ⁰C. The alloy substrate is taken out from the solution and cleaned when the anodizing is completed.

(2) Preparation of the sealing reagent About 60 g sodium dodecyl sulfonate, 15 g sodium naphthylmethylene sulfonate, 15 g siloxane, 3O g sodium acetate and an appropriate amount of deionized water are mixed to obtain about 1000 g sealing reagent.

(3) Sealing The aluminum alloy treated in step (1) is placed into the sealing reagent of step (2) with an initial concentration of about 0.7 ml/L at about 85 ⁰C for about 15 minutes. Then it is dried in baking oven at about 60 ⁰C for about 15 minutes.

EXAMPLE 2 (1) Anodizing of 5056 aluminum alloy

A 5056 aluminum alloy is used as a substrate to anodize. The former steps are similar to those used in step (1) of Example 1, with the further dyeing process after anodizing: the substrate is placed into a dyeing solution for about 2-15 minutes. The concentration of the dyeing solution is about 1-10 g/L; the pH is about 6; the dosage is about 6 g per sq.m. substrate; and the temperature of the dyeing solution is about 50⁰C. The substrate is taken out from the dyeing solution and cleaned after dyeing.

(2) Preparation of the sealing reagent

About 30 g sodium dodecyl sulfonate, 1O g dispersing agent CNF, 20 g siloxane, 50 g sodium citrate and an appropriate amount of deionized water is mixed to obtain about 1000 g sealing reagent.

(3) Sealing

The aluminum alloy treated in step (1) is placed into the sealing reagent of step (2) with an initial concentration of about 1.5 ml/L at about 87 ⁰C for about 20 minutes. Then it is dried in baking oven at about 60 ⁰C for about 15 minutes. EXAMPLE 3

(1) Anodizing of 7003 aluminum alloy

A 7003 aluminum alloy is used as a substrate to anodize. The steps are similar to those used in step (1) of Example 2. (2) Preparation of the sealing reagent

About 100 g sodium cetyl benzene sulfonate, 20 g methyl naphthalenesulfonate/ formaldehyde condensation polymer, 1O g siloxane, 1O g sodium dihydrogen phosphate and an appropriate amount of deionized water are mixed to obtain about 1000 g sealing reagent.

(3) Sealing

The aluminum alloy treated in step (1) is placed into the sealing reagent of step (2) with an initial concentration of about 4 ml/L at about 91 ⁰C for about 30 minutes. Then it is dried in baking oven at about 60 ⁰C for about 15 minutes.

EXAMPLE 4

(1) Anodizing of 6061 aluminum alloy

A 6061 aluminum alloy is used as a substrate to anodize. The steps are similar to those used in step (1) of Example 2. (2) Preparation of the sealing reagent

About 50 g sodium cetyl benzene sulfonate, 18 g methyl naphthalenesulfonare/ formaldehyde condensation polymer, 12 g siloxane, 16 g disodium hydrogen phosphate and an appropriate amount of deionized water are mixed to obtain about 1000 g sealing reagent. (3) Sealing

The aluminum alloy treated in step (1) is placed into the sealing reagent of step (2) with an initial concentration of about 8 ml/L at about 95 ⁰C for about 40 minutes. Then it is dried in baking oven at about 60 ⁰C for about 15 minutes.

REFERENCE 1 (1) Anodizing of 6061 aluminum alloy

A 6061 aluminum alloy is used as a substrate to anodize. The steps are similar to those used in step (1) of Example 1.

(2) Sealing The aluminum alloy treated in step (1) is placed into a sealing reagent (TOP

DX-500, with the main ingredient of nickel acetate, OKUNO New Technology

Industries (Hangzhou) Co. Ltd, China) with a concentration of about 7 g/L at about

90 ⁰C for about 20 minutes. Then it is dried in baking oven at about 60 ⁰C for about 15 minutes.

TESTING

(l)Nickel Content, Nickel Releasing, Corrosion Resistance and Wear Resistance Tested according to the method in BS EN12472: 2005, the nickel content and nickel releasing results of the products after sealing in EXAMPLE 4 and REFERENCE 1 are shown in Table 1. And the salt mist corrosion resistance and wear resistance of the products after sealing in EXAMPLE 4 and REFERENCE 1 are tested according to the standards of ISO9227-1990 and ASTM F2357-04. The results are shown in Table 1 too.

Table 1. Nickel Content, Nickel Releasing, Corrosion Resistance and Wear Resistance of EXAMPLE 4 and REFERENCE 1

From Table 1, it can be observed that the 6061 aluminum alloy treated by the nickel-free sealing reagent of EXAMPLE 4 contains substantially no more nickel than the substrate itself does before being treated by the nickel-free sealing reagent. In contrast, the 6061 aluminum alloy treated by the nickel-containing sealing reagent of Reference 1 contains substantially more nickel than the substrate itself does before being treated by the nickel-containing sealing reagent. The reliability performances, namely salt mist corrosion resistance and wear resistance, of the 6061 aluminum alloy treated by the nickel-free sealing reagent are similar to the 6061 aluminum alloy treated by the nickel-containing sealing reagent.

(2) Weight Loss The sealing effect can be assessed in a weight loss test. Following the standards of GB/T5237.2-2000, a spot on the surface of samples is wiped clean. A proper organic solution is used to degrease the samples at room temperature. After drying and weighing, the samples are placed into a mixture of phosphoric acid and chromic acid at about 38±1°C for about 15 minutes. The samples are taken out of the mixture, and weighed again after washing and drying to calculate the weight loss. The weight losses of the products after sealing in EXAMPLE 1-4 and REFERENCE 1 are shown in Table 2.

Table 2. Weight Loss of EXAMPLE 1 -4 And REFERENCE 1

The sealing is qualified if the weight loss is less than about 20 mg/dm . From Table 2, it can be observed that the weight losses of aluminum alloys in EXAMPLE 1-4 are all less than about 7.0 mg/dm which means all the sealing reagents of the present disclosure are qualified and can be used in industry.

Although the present disclosure has been described in detail with reference to several embodiments, additional variations and modifications exist within the scope and spirit as described and defined in the following claims.

Claims

WHAT IS CLAIMED IS:

LA nickel-free sealing reagent, comprising: an alkyl sodium sulfonate compound; a dispersing agent; and a siloxane defoaming agent.

2. The nickel-free sealing reagent of claim 1, wherein the alkyl sodium sulfonate compound comprises one or more compounds selected from the group consisting of sodium dodecyl sulfonate, sodium dodecyl benzene sulfonate, sodium cetyl sulfonate, and sodium cetyl benzene sulfonate.

3. The nickel-free sealing reagent of claim 1, wherein the dispersing agent comprises one or more compounds selected from the group consisting of sodium naphthylmethylene sulfonate, benzyl naphthalenesulfonate/formaldehyde condensation polymer, and methyl naphthalenesulfonate/ formaldehyde condensation polymer.

4. The nickel-free sealing reagent of claim 1, wherein the siloxane defoaming agent comprises one or more compounds selected from the group consisting of polydimethylsiloxane, polyether modified polysiloxane, ethoxyl modified trisiloxane, and siloxane-oxyalkylene copolymers.

5. The nickel-free sealing reagent of claim 1, further comprising a buffering agent.

6. The nickel-free sealing reagent of claim 5, wherein the buffering agent comprises one or more compounds selected from the group consisting of sodium acetate, disodium hydrogen phosphate, sodium dihydrogen phosphate, and sodium citrate.

7. The nickel-free sealing reagent of claim 5, wherein the buffering agent accounts for about 1 weight percent to about 5 weight percent of the sealing reagent.

8. The nickel-free sealing reagent of claim 1, wherein the alkyl sodium sulfonate compound accounts for about 3 weight percent to about 10 weight percent of the sealing reagent.

9. The nickel-free sealing reagent of claim 1, wherein the dispersing agent accounts for a.bout 1 weight percent to about 2 weight percent of the sealing reagent.

10. The nickel-free sealing reagent of claim 1, wherein the siloxane defoaming agent accounts for about 1 weight percent to about 2 weight percent of the sealing reagent.

11.The nickel-free sealing reagent of claim 1, which has a pH of from about 5 to about 6.5.

12. The nickel-free sealing reagent of claim 1, which is an aqueous solution.

13. A method of sealing an alloy, comprising: applying a nickel-free sealing reagent to the alloy, wherein the sealing agent comprising an alkyl sodium sulfonate compound; a dispersing agent; and a siloxane defoaming agent.

14. The method of claim 13, wherein the alkyl sodium sulfonate compound comprises one or more compounds selected from the group consisting of sodium dodecyl sulfonate, sodium dodecyl benzene sulfonate, sodium cetyl sulfonate, and sodium cetyl benzene sulfonate.

15. The method of claim 13, wherein the dispersing agent comprises one or more compounds selected from the group consisting of sodium naphthylmethylene sulfonate, benzyl naphthalenesulfonate/formaldehyde condensation polymer, and methyl naphthalenesulfonate/ formaldehyde condensation polymer.

16. The method of claim 13, wherein the siloxane defoaming agent comprises one or more compounds selected from the group consisting of polydimethylsiloxane, polyether modified polysiloxane, ethoxyl modified trisiloxane, and siloxane-oxyalkylene copolymers.

17. The method of claim 13, wherein the nickel-free sealing reagent further comprises a buffering agent.

18. The method of claim 17, wherein the buffering agent comprises one or more compounds selected from the group consisting of sodium acetate, disodium hydrogen phosphate, sodium dihydrogen phosphate, and sodium citrate.

19. The method of claim 13, wherein the alloy is an aluminum alloy.

20. The method of claim 13, wherein the applying comprises immersing the alloy in the nickel-free sealing reagent.