Anodizing Aluminum
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Revision as of 22:17, 29 January 2010
Contents |
Meta-Bits
- Organizer
- punkin
- Participants
- Date
- (Date not set) 2010
- Comment
- This document is a very messy, poorly edited, and unreliable work-in-progress. I failed high school chemistry; any or all of the info here may be wrong.
Goal
Aluminum is cheap (yay!), but its also soft, and worse, its dirty. Through the magic of electricity (and a wee bit of chemistry), we can harden aluminum's surface, increase its resistance to corrosion, and as a by-product, persuade it to take up dye -- pretty!
Theory
Preparing the Aluminum
Grease and grime on the surface of the aluminum will interfere with the anodizing process. (Why?)
Aluminum is a self-protecting metal: when exposed to oxygen, it builds up a relatively inert, "dirty" oxide layer. This oxide layer can be cleaned, but the surface will re-oxidize as soon as fresh metal is exposed.
In order to anodize our aluminum, we first need to clean the aluminum, and remove this oxide layer.
I think we don't need to remove the oxide layer entirely; just ensure that its minimal. We also need to remove all other contaminants, such as grease, from the surface.
- Cleaning with dish soap
- Provided the aluminum hasn't all ready been anodized, and you don't want to etch it (to create a matte finish), dish soap and hot water should remove all grease, and enough of the oxide layer for anodizing to take place.
- Cleaning with Sodium Hydroxide
- For stronger cleaning power, NaOH will dissolve any and all organic matter (including the thickest layers of oxide) from the aluminum. You can tell when its dissolved through, because the exposed aluminum will begin reacting to the water in the solution, by releasing hydrogen gas. 5% NaOH at 140F will break through the oxide and start to gas hydrogen in about 10 minutes.
- A side effect of the NaOH "deep cleaning" is that the aluminum surface will become etched. This may be a desirable effect, and will result in a more matte finish.
- Some sources recommend pre-washing in dish soap before using the NaOH solution. Others recommend following the NaOH bath with dish soap. I'm not clear on the benefit of either of these approaches.
- Some sources also talk abut desmutting the aluminum after the NaOH bath; I don't know what this is all about yet. Not everyone seems to do it.
Anodizing the Aluminum
Dying the Aluminum
Sealing the Aluminum
Practice
Materials
Safety Equipment
- Sodium Bicarbonate
- nitrile gloves
- safety glasses
Preparing the Aluminum
(Sodium Hydroxide solution can be re-used for years, if protected from cross-contamination between steps. Add more water to bring the level back up as it evaporates)
- Sodium Hydroxide (NaOH) solution
- dish soap
- hot water
- 5 gallon plastic tub or cooler
Anodizing the Aluminum
(Sulfuric Acid solution can be re-used for years, if protected from cross-contamination between steps. Add more water to bring the level back up as it evaporates)
- 15-20% Sulfuric Acid (H2SO4) solution
- 12 volt power supply
- 5 gallon plastic tub or cooler
- lead cathode
- aluminum wire
Dying the Aluminum
(Dying solution can be re-used for years, if protected from cross-contamination between steps. Add more water to bring the level back up as it evaporates)
- prepared fabric dye solution in desired color (i.e., Dylon)
- large container (metal pot, plastic storage container or cooler)
- heat source (burner, if using a metal pot; aquarium heater, if using plastic)
Sealing the Aluminum
- distilled water
- large pot
- burner large enough for the pot, and hot enough to bring water to a boil
Method
Preparing the Aluminum
Anodizing the Aluminum
Dying the Aluminum
Sealing the Aluminum
Safety
This project involves working with chemicals that can hurt you very badly and very permanently. Before you begin, make sure you have a copy of the MSDS from the manufacturer of your chemicals, have read and understood it, and are following all of the recommended guidelines for safe use, safe storage, and safe disposal. Use protective equipment (gloves, safety clothing, and eye protection) at all times.
Sodium Hydroxide (NaOH)
Sodium Hydroxide is corrosive; if it comes into contact with unprotected human tissue, it will burn very badly, and cause permanent scarring.
- MSDS
- JTBaker
- R-Phrases
- R35
- S-Phrases
- S1/2, S26, S37/39, S45
Sulfuric Acid (H2SO4)
Sulfuric Acid is corrosive; if it comes into contact with unprotected human tissue, it will burn very badly, and cause permanent scarring.
In addition to being corrosive, sulfuric acid has a highly exothermic reaction with water. If you get it on your skin, the heat created by this reaction will cause further burning.
Finally, it will also suck out enough moisture from your skin to cause tissue damage.
- MSDS
- Wikipedia
- R-Phrases
- R35
- S-Phrases
- S1/2, S26, S30, S45
Resources
Materials
- Sodium Bicarbonate
- Any grocery store will sell this as baking soda. We want to have lots on hand, just in case, so look for grocery stores which will let you buy it in bulk. I.e., The Bulk Barn.
- Sodium Hydroxide
- Home Hardware sells a product called Home Lye Crystals (available with the drain cleaners), for about $22/3Kg container. This product is guaranteed to be 90-98% pure Sodium Hydroxide; it contains trace amounts of "something to keep it from clumping", which is not a problem for our purposes.
- biobar/Tekniscience, out of Quebec sells different concentrations of Sodium Hydroxide online. I have not purchased from them before. There may or may not be a HazMat handling fee.
- Sulfuric Acid
- biobar/Tekniscience, out of Quebec sells different concentrations of Sulfuric Acid online. I have not purchased from them before. There may or may not be a HazMat handling fee.
