METHOD FOR ANODIZING AND DYEING METALLIC ARTICLE

1. Technical Field

The present disclosure generally relates to methods foranodizing and dyeing metallic articles.

2. Description of Related Art

Metallic articles, such as articles made of aluminum/aluminum alloy, magnesium/magnesium alloy, and titanium/titanium alloy, are usually applied with an anodizing treatment, such that anodization layers are formed on the surfaces of the metallic articles to protect the metallic articles. To provide a color to the metallic articles to appear more colorful, after the anodizing treatment, the metallic articles may be applied with a dyeing treatment or a painting treatment. However, the color of the metallic article obtained may be in only one color, and also cannot produce a gradual color change or color gradient appearance.

Therefore, there is room for improvement within the art.

FIG. 1 shows a workpiece 100 according to an illustrated embodiment to be anodized and dyed by a method for anodizing and dyeing a metallic article. The workpiece 100 is a metallic article made of aluminum alloy, and is substantially rectangular plate-like in shape. The workpiece 100 includes a decorated surface 10 to be dyed. In other embodiments, the workpiece 100 can be made of aluminum, magnesium, magnesium alloy, titanium, or titanium alloy.

Referring also to FIG. 6, an embodiment of a method for anodizing and dyeing the workpiece 100 of the illustrated embodiment of FIG. 1 is described as follows.

In step S101, the workpiece 100 is applied with one or more pre-anodizing treatments, for smoothing and texturing the decorated surface 10, and/or removing grease residues or a native oxide layer on the decorated surface 10. The one or more pre-anodizing treatments may include one or more of polishing, texturing, degreasing, alkaline etching, and desmutting. A degreasing solution used for performing degreasing of the grease residues is a weak alkaline solution, such as sodium pyrophosphate solution. An alkaline etching solution used for alkaline etching is a strong alkaline solution, such as a sodium hydroxide solution. A desmutting solution used for desmutting is a strong acid solution. Examples of polishing may include chemical polishing or mechanical polishing. Examples of texturing may include sandblasting or wiredrawing.

In step S102, the workpiece 100 is anodized by an anodizing treatment, such that an anodization layer 20 is formed on the decorated surface 10. The anodization layer 20 is porous having a plurality of holes 30 therein. The holes 30 have a substantially uniform depth (referring to FIG. 2). The anodizing treatment may be a direct current anodizing treatment, an alternating current anodizing treatment, or a pulse current anodizing treatment. In an illustrated embodiment, the direct current anodizing treatment is applied to the workpiece 100. The workpiece 100 as an anode is electrically connected with a positive electrode, and a sulfuric acid solution is used as an electrolyte solution, such that the anodization layer 20 is formed on the decorated layer 10. A thickness of the anodization layer 20 and a depth of the holes 30 can be changed by an anodization time, a current value, or a voltage value. In other embodiments, the electrolyte solution may include nitrate ion, phosphate ion, chromate ion, or silicateion.

In step S103, the workpiece 100 is sealed by a first sealing treatment in a first sealing solution 200. During the first sealing treatment, a contacting time (duration) of the anodization layer 20 and the first sealing solution 200 gradually changes along a predetermined direction, such that the depth of the holes 30 gradually changes along the predetermined direction after the first sealing treatment. In the illustrated embodiment, referring to FIGS. 3 through 5, the anodization layer 20 is configured substantially perpendicular to a liquid level 201 of the first sealing solution 200, and the workpiece 100 is immersed into the first sealing solution 200 at a predetermined velocity, and then taken out of the first sealing solution 200. The contacting time of the anodization layer 20 and the first sealing solution 200 gradually increases along a moving direction of the workpiece 100 during the first sealing treatment, and thereby an amount of a sealing agent 40 of the first sealing solution 200 entering into each of the holes 30 gradually increases along the moving direction of the workpiece 100 (referring to FIG. 5, a portion of the anodization layer 20 having larger amount of the sealing agent 40 enters into the first sealing solution 200 earlier than another portion of the anodization layer 20 having lesser amount of the sealing agent 40. Thus, the depth of the holes 30 gradually decreases along the moving direction of the workpiece 100. The sealing agents 40 of the first sealing solution 200 can be nickel acetate, nickel sulfate, or cobalt sulfate. The predetermined velocity of the workpiece 100 immersed into the first sealing solution 200 can be constant, or changing. When the predetermined velocity of immersion of the workpiece 100 is kept constant, the depth of the holes 30 decreases uniformly along the moving direction of the workpiece 100. If the predetermined velocity of immersion of the workpiece 100 changes, the depth of the holes 30 will decreases non-uniformly along the moving direction of the workpiece 100. In other embodiments, the contacting time of the anodization layer 20 and the first sealing solution 200 can change gradually along the predetermined direction in other ways. For example, the first sealing solution 200 is sprayed on the anodization layer 20 by a sprayer connected to the first sealing solution 200, and a spraying time is controlled along the predetermined direction.

In step S104, the workpiece 100 is colored by a dyeing treatment. In the dyeing treatment, a coloring agent enters into the holes 30 to dye the decorated layer 10. Because the depth of the holes 30 decreases gradually along the predetermined direction, an amount of the coloring agent entering into the holes 30 thereby decreases gradually along the predetermined direction. Thus, the anodization layer 20 is colored with a gradual changing color or color gradient.

In step S105, the workpiece 100 is sealed by a second sealing treatment in a second sealing solution (not shown). In the second sealing treatment, the workpiece 100 is immersed into the second sealing solution to seal the holes 30, such that the anodization layer 20 has a good wear resistance.

In step S106, the workpiece 100 is dried by heating.

In other embodiments, if the workpiece 100 is cleaned or a texturing effect is not needed, step S101 can be omitted. Step S105 can be omitted if a required wear resistance of the workpiece is low. Step S106 can be omitted if desired, and the workpiece can be air dried instead.

The contacting time of the anodization layer 20 and the first sealing solution 200 changes gradually along the predetermined direction, such that the depth of the holes 30 after the first sealing treatment changes gradually along the predetermined direction, and the amount of the coloring agent 40 entering into the holes 30 during the dyeing treatment thereby changes gradually along the predetermined direction. Thus, the anodization layer 20 after the dyeing treatment has a gradual changing color or color gradient. The above-described method for anodizing and dyeing a metallic article is easy to control, and thus is suitable for mass production.

Depending on the embodiment, some of the steps being described may be removed or eliminated, while other steps may be added, and the sequence of steps may be changed. It is also to be understood that the description and the claims drawn to a method may include some indication in reference to certain steps. However, the indication used is only to be viewed for identification purposes and not as a suggestion as to an order for the steps.

It is to be understood, however, that even through numerous characteristics and advantages of the disclosure have been set forth in the foregoing description, together with details of the structure and function of the present disclosure, 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 present disclosure to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.