Aluminum anode and stained aluminum with battery acid
Aluminum anodes and aluminum staining of aluminum fixed parts in many details have long been common. But the use of battery acids, typically (29% to 32% sulfuric acid) causes concern and reluctance, and prohibits others from even trying to anodize aluminum at home. It can be difficult to store, dangerous to skin and clothing, and in general, not fun to work with. OSHA lists it as corrosive. This project offers an alternative to using liquid sulfuric acid and alternative uses, a granular pool chemical that is easy to find, mix, store and work with. OSHA lists this chemical as only a stimulant with no shipping limits.
The disposal is easy using baking soda for neutralization and the results are comparable to using the sulfuric acid method. An alternative chemical is sodium bisulfate (NaHSO4) the sodium salt of sulfuric acid but in a weaker form. It is also known as sodium sodium sulfate and is used to reduce ph in home swimming pools. As in the use of any chemicals, care and caution are in order.
Aluminum and some other metals have a barrier coating that naturally occurs as a result of a reaction with oxygen in the air. In the case of aluminum, that barrier is aluminum oxide, Al2O3. All processed aluminum has this coating. But, it has long been known that using a metal electrolysis process can provide additional protection.
There are generally two types of barrier coatings. The first is a thin, hard coating that increases hardness and insulation properties. The second is a porous cell structure that allows a dye to fill cells and provide a decorative and protective coating. This is the structure required for this project. After the dye has filled the cells that have been color anodized, the flakes are placed in boiling water for 20 to 30 minutes to completely seal the dye.
Sodium Bisulfate, NaHSO4, also known as Sodium Hydrogen Sulfate. The pool additive used is Aqua Chem + balanced + protected-down pH. I found this and similar products to lower the pH of swimming pools in both garden centers and hardware stores. Find the chemical name and at least 90% of the active ingredient.
Sodium hydroxide. (Optional) NaOH is also called a clean drain or an alkaline solution, available at all hardware stores.
RIT liquid dye. I used many colors but only in concentrated liquid form. The dry datagrams might work but I haven’t tried them yet. Available in grocery, drug and hardware stores.
Battery or DC power current. A 1.5 volt D cell can be used. I used a rechargeable 6 volt battery but a fart on the wall would work fine too. This project prefers relatively low voltage and current less than 400mA for these small parts. Slow anodizing seems to work best. Voltage and current guidelines for the larger sections will be listed in the comments section.
· Aluminum or Lead for the cathode. (The battery lead is negative). Both are essentially inert in this chemical. Some aluminum will be deposited into the cathode but it can be easily removed.
· Aluminum metal to anodize.
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Aluminum anodes and aluminum staining of aluminum fixed parts in many details have long been common. But the use of battery acids, typically (29% to 32% sulfuric acid) causes concern...Xem chi tiết →