SOLUTION FOR REMOVING TITANIUM-CONTAINING COATINGS AND METHOD FOR SAME

Abstract

A solution and method for removing titanium-containing coatings from the surface of substrates using the solution are provided. The solution includes 90-1000 g/L organic or inorganic acid; 70-500 g/L accelerant, the accelerant being acid or salt which contains fluorinion; 15-200 g/L secondary accelerator, the secondary accelerator being generic amino alcohols which can combine with titanium ion; 2-8 g/L inhibiter, the inhibiter being selected from one or more of the group consisting of thiourea, thiourea derivatives, and carbamide. The method for removing titanium-containing coating on the substrate mainly includes contacting the substrate with the titanium-containing coating with the solution.

Description

BACKGROUND

1. Technical field

The present disclosure relates to a solution for removing titanium-containing coatings and a related method.

2. Description of related art

Hard ceramic coatings, such as titanium nitride and titanium carbide, impart specific properties to workpieces such as machining tools, die core-pins, and high temperature devices. These hard coatings resist wear, abrasion, oxidation, and corrosion, and reduce susceptibility to chemical reactions on the workpieces to which they are applied. These coatings, however, can fail locally during use or manufacture.

Often, when such coatings fail, the entire die or tool component is discarded even if the underlying substrate shows no damage, at considerable cost. For this reason, the ability to recycle the underlying substrate by removing a failed coating and replacing it with a new coating is economically preferable.

Therefore, there is room for improvement within the art.

DETAILED DESCRIPTION

The present disclosure relates to a solution and a related method for removing titanium-containing coatings formed on the surfaces of substrates. The titanium-containing coating may be titanium nitride coating, titanium carbide coating, or titanium carbonitride coating. The substrate may be metal or plastic. The metal may be ferric-based alloy, copper, or copper alloy.

The solution may be an aqueous solution containing acid, accelerant, secondary accelerator, and inhibiter.

The acid may be inorganic acid or organic acid providing hydrogen ions, such as sulphuric acid, acetic acid, citric acid, or lactic acid, or a combination thereof. In an exemplary embodiment, sulphuric acid can be selected. The concentration of the acid selected may be about 90-1000 g/L, and is in this exemplary embodiment it is about 90-750 g/L.

The accelerant may speed dissolution of metallic ions of the titanium-containing coatings into the solution. The accelerant may be acid or salt which contains fluorinion. The accelerant may be hydrofluoric acid, ammonium bifluoride, sodium fluoride, potassium fluoride, sodium fluoborate, or zirconium sodium fluoride, or a combination thereof, and in this exemplary embodiment it is hydrofluoric acid and/or ammonium bifluoride. The concentration of the accelerant selected may be about 70-500 g/L and in this exemplary embodiment it is about 75-300 g/L.

The secondary accelerator can diminish the surface tension of the solution, facilitate the dissolving of the coatings, and accelerate the penetration of the hydrogen ion. The secondary accelerator may be generic amino alcohols and can combine with titanium ion. For example, the secondary accelerator may be ethanolamine, diethanolamine, or triethanolamine, or a combination thereof, and in this exemplary embodiment it is triethavolamine. The concentration of the secondary accelerator selected may be about 15-200 g/L, and in this exemplary embodiment it is about 30-80 g/L.

The inhibiter protects the substrate from being etched by the acid. The inhibiter may be thiourea, thiourea derivatives, or carbamide, or a combination thereof, and in this exemplary embodiment it is thiourea or thiourea derivatives. The concentration of the inhibiter selected may be about 2-8 g/L, and in this exemplary embodiment it is about 3-5 g/L.

The solution may be prepared by dissolving the acid, accelerant, secondary accelerator, and inhibiter in water.

The method for removing the titanium-containing coating formed on the substrate may include steps of providing the solution, and contacting the substrate combined with a titanium-containing coating to the solution. The coating can be effectively removed from the substrate and the underlying base is free from damage by the present method. The substrate may contact the solution by immersion or spraying. The solution may have a temperature of about 20-30° C. Contact time between the substrate and the solution may be 0.5-2 hours. After contact, the substrate may be rinsed with water and then dried.

EXAMPLES

Experimental examples of the present disclosure are described as followings.

Example 1

1. Preparation of the Solution

50ml sulphuric acid having a concentration of 98 wt % and 5 g thiourea was added into 500 ml deionized water. Then, 200 ml hydrofluoric acid having a concentration of 40 wt % and 50 ml triethanolamine having a concentration of 80 wt % were added into the water solution. The water solution was supplemented with deionized water to 1000 ml. The solution was formed and contained the sulphuric acid with a concentration of about 90.16 g/L; the hydrofluoric acid with a concentration of about 90.4 g/L; the triethanolamine with a concentration of about 40.8 g/L.

2. Removal of Titanium-Containing Coatings

Samples of stainless steel substrate were provided. The stainless steel substrate had a coating selected from one of the titanium nitride coating, titanium carbide coating, and titanium carbonitride coating. The coating had a thickness of about 2 μm. The samples were completely immersed in the solution for about 1.5 hours at a temperature of about 25° C. During this process, the coatings were removed. Then, the samples were taken out of the solution and were dried after being rinsed with water.

Example 2

1. Preparation of the Solution

55 ml sulphuric acid having a concentration of 98 wt % and 5 g thiourea was added into 500 ml deionized water. Then, 175 ml hydrofluoric acid having a concentration of 40 wt % and 54 ml triethanolamine having a concentration of 80 wt % were added into the solution. The solution was supplemented with deionized water to 1000 ml. The solution was formed and contained the sulphuric acid with a concentration of about 99.18 g/L; the hydrofluoric acid with a concentration of about 79.11 g/L; the triethanolamine with a concentration of about 44.88 g/L.

2. Removal of Titanium-Containing Coatings

Samples of stainless steel substrate were provided. The stainless steel substrate had a titanium carbide coating. The coating had a thickness of about 1.5 μm. The samples were completely immersed in the solution for about 1 hour at a room temperature. During this process, the coating was removed. Then, the samples were taken out of the solution and were dried after being rinsed with water.

Example 3

1. Preparation of the Solution

400 g ammonium bifluoride and 5 g thiourea was dissolved in 500 ml deionized water. Then, 400 ml acetic acid having a concentration of 36 wt % and 20 ml triethanolamine having a concentration of 80 wt % were added into the water solution. The solution was formed and contained the acetic acid with a concentration of about 90.16 g/L; the hydrofluoric acid with a concentration of about 145 g/L; the triethanolamine with a concentration of about 16.32 g/L.

2. Removal of Titanium-Containing Coatings

Samples of stainless steel substrate were provided. The stainless steel substrate had a titanium carbonitride coating. The coating had a thickness of about 2 μm. The samples were completely immersed in the solution for about 2 hours at a room temperature. During this process, the coating was removed. Then, the samples were taken out of the solution and were dried after being rinsed with water.

Examples 4-6

In examples 4-6, the solutions were respectively prepared according to the examples 1-3. Unlike the examples 1-3, the stainless steel substrate of the samples was replaced with copper substrate. Except the above difference, the remaining experiment conditions of examples 4-6 were respectively same with examples 4-6.

Results of the Examples 1-6

The samples processed in the examples 1-6 were inspected by X-ray diffraction (X-RD). No titanium was detected on the of samples. Accordingly, the coatings were effectively and completely removed from the underlying base. Furthermore, the processed samples were tested by scanning electronic microscopy (SEM). The scanning indicated no damage found to the underlying bases.

It is to be understood, however, that even though numerous characteristics and advantages of the present embodiments have been set forth in the foregoing description, together with details of the structures and functions of the embodiments, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.

Claims

1. An aqueous solution for removing titanium-containing coatings on substrate surface, comprising: 90-1000 g/L organic or inorganic acid;70-500 g/L accelerant, the accelerant being an acid or salt containing fluorinion;15-200 g/L secondary accelerator, the secondary accelerator being generic amino alcohols and can combine with titanium ion; and2-8 g/L inhibiter, the inhibiter selected from one or more of the group consisting of thiourea, thiourea derivatives, and carbamide.

2. The aqueous solution as claimed in claim 1, wherein the acid is selected from one or more of the group consisting of sulphuric acid, acetic acid, citric acid, and lactic acid.

3. The aqueous solution as claimed in claim 2, wherein the acid is sulphuric acid or acetic acid.

4. The aqueous solution as claimed in claim 1, wherein the concentration of the acid is about 90-750 g/L.

5. The aqueous solution as claimed in claim 1, wherein the accelerant is selected from one or more of the group consisting of hydrofluoric acid, ammonium bifluoride, sodium fluoride, potassium fluoride, sodium fluoborate, and zirconium sodium fluoride.

6. The aqueous solution as claimed in claim 5, wherein the accelerant is hydrofluoric acid and/or ammonium bifluoride.

7. The aqueous solution as claimed in claim 1, wherein the concentration of the accelerant is about 75-300 g/L.

8. The aqueous solution as claimed in claim 1, wherein the secondary accelerator is selected from one or more of the group consisting of ethanolamine, diethanolamine, and triethanolamine.

9. The aqueous solution as claimed in claim 1, wherein the concentration of the secondary accelerator is about 30-80 g/L.

10. The aqueous solution as claimed in claim 1, wherein the inhibiter is thiourea or thiourea derivatives.

11. The aqueous solution as claimed in claim 1, wherein the concentration of the inhibiter is about 3-5g/L.

12. A method for removing titanium-containing coating on substrate, comprising: providing an aqueous solution, the aqueous solution containing 90-1000 g/L organic or inorganic acid, 70-500 g/L accelerant, the accelerant being an acid or salt containing fluorinion, 15-200 g/L secondary accelerator, the secondary accelerator being generic amino alcohols and can combine with titanium ion, and 2-8 g/L inhibiter, the inhibiter being selected from one or more of the group consisting of thiourea, thiourea derivatives, and carbamide; andcontacting the substrate with the titanium-containing coating with the aqueous solution.

13. The method as claimed in claim 12, wherein the acid is selected from one or more of the group consisting of sulphuric acid, acetic acid, citric acid, and lactic acid.

14. The method as claimed in claim 12, wherein the accelerant is selected from one or more of the group consisting of hydrofluoric acid, ammonium bifluoride, sodium fluoride, potassium fluoride, sodium fluoborate, and zirconium sodium fluoride.

15. The method as claimed in claim 12, wherein the secondary accelerator is selected from one or more of the group consisting of ethanolamine, diethanolamine, and triethanolamine.

16. The method as claimed in claim 12, wherein the aqueous solution has a temperature of about 20-30° C., the contact time between the substrate and the aqueous solution is about 0.5-2 hours.

17. The method as claimed in claim 12, wherein the substrate is made of metal or plastic.

18. The method as claimed in claim 17, wherein the metal is one of the ferric-based alloy, copper, and copper alloy.

19. The method as claimed in claim 12, wherein the titanium-containing coating is titanium nitride coating, titanium carbide coating, or titanium carbonitride coating.

20. The method as claimed in claim 12, wherein the substrate contacts the aqueous solution by immersion or spraying.