However, this type of parts are not recommended for applications with thermal shocks due to the loss of flexibility suffered by the material during anodizing.
The reason lies in the properties of the metal itself, such as its surface hardness, which makes it resistant to scratching, its thermal conductivity, the possibilities of colouring and, as we saw in the post about the aluminium composite panel , the possibility of aluminium being recycled in an unlimited way.
This type of colouring is done through metal oxides that are fixed in the alumina layer by means of alternating current. In this type of colouring, the metal ions are deposited at the bottom of the pores of the layer. The final tone and brightness will depend on the distribution of the metal, which is achieved according to the metallic salts used.
For example, with Cu copper salts, reddish tones are obtained. Coloration is achieved through the use of direct current.
The tones achieved will be solid and will go from bronze and light grey to bronze and dark grey. The final result is an oxide layer that is harder and more resistant to abrasion than in the case of electrolytic colouring. With this type of process, the colour range that can be achieved is substantially extended. In this case, the electrolytically coloured oxide layers can be re-coloured with organic or inorganic dyes , maintaining the metallic effect.
Aluminium is classified in series according to its hardness and alloy. The larger the series, the harder the material. Since the entire range of color for the titanium oxide layer is within 25 billionths of a meter a nanometer is 1-billionth of a meter , it is little wonder that the process requires careful precision and high-quality anodizing equipment to reach the best results.
It should be noted that not every color can be produced with titanium anodizing. In particular, red anodized titanium is not possible due to the physics of the optical interference phenomenon. The nearest available colors to red would be magenta, rose reddish violet or purple. In Type 3 color anodizing, a titanium part is immersed in an electrolyte solution.
The most common chemistry uses trisodium phosphate TSP , forming an alkaline solution; however, there are many options. The chemistry serves to provide ions for the electrolytic process, but it does not directly affect the titanium surface. The electrical part of the anodizing process requires a specialized rectifier , an electrical device that converts alternating current AC to direct current DC.
The rectifier allows you to regulate the voltage to a level that you specify and to control the amperage. In titanium anodizing, the voltage dictates the color. The volt range for color titanium anodizing is between 15 and volts. A bronze color, with the thinnest oxide layer, can be achieved with about 16 volts. A green color, with the thickest oxide layer, can be achieved with volts. In contrast, the amperage dictates the time required.
By increasing the amperage, the oxide layer forms more quickly. But the increased amperage carries a risk of inconsistency in color output, because it can become too difficult to stop the oxide layer buildup at the correct color.
Product size drives the amperage; typically, the larger the product, the more amperage is used. Best Technology and its partners have developed custom chemical blends of solutions and electrolytes that greatly increase the manufacturing yield of this process, which are not offered by anyone else in the industry. The chemistry for a titanium anodizing line includes both cleaning and electrochemical electrolytes. For manufacturers looking to take their titanium color anodizing in-house and build their own Type 3 color anodize line, here is an example of process steps:.
Surface preparation , also called anodize prep, is crucial for achieving consistent color for titanium. The titanium surface must be prepared in a way that supports the even distribution of the oxide layer. Anodize prep requires removing a thin layer of material to create a uniform surface for color anodizing.
The titanium grade determines the level of prep; the purer grades of titanium such as grade 2 require more aggressive surface prep than titanium alloys such as grade 5, titanium 6AI-4V. Timing is critical after surface preparation. The anodize process should occur almost immediately after the anodize prep. Otherwise within hours of exposure to oxygen air, water the oxide layer will form apart from anodizing. Anodizing parts after the oxide layer has already formed results in a splotchy color pattern that is not desirable.
Surface finish is one of the biggest factors that can affect the appearance of color. If the part is machined poorly, some of the surface areas can become work-hardened or smeared. Upon application of electricity, the work-hardened or smeared area slows down the electrical current, and the resulting color is inconsistent and not harmonious. The deeper the pores, the rougher the surface will be but the colors will also be that much more durable.
Secondly, light striking the surface partly interacts with the colorant and partly with the uncolored metal at the top. Light changes colors as it reflects from an anodized surface.
So the light that bounces back to strike your eye will in fact be a combination of two distinct wavelengths interacting as they reflect from slightly different surfaces. This causes the distinctive shine of aluminum anodizing. Anodizing also works with magnesium, titanium and even conductive plastics.
Anodizing requires that a part is immersed in a series of chemical baths. Holding a part in position requires that it be mounted on a hanger of some kind to keep it from falling to the bottom of the tank. Our specialists will help you to find the solution that fits your budget, time to market and desired results.
He is passionate about writing and about developments in science, manufacturing and related technologies. He is also a certified English grammar snob. Request a Quote. Subscribe to Our Newsletter Receive industry related information about product development and manufacturing straight to your inbox. Thanks for signing up! Sign Up. Anodizing is functional and beautiful. Chris Williams. Share this post.
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