Instructables

Anodizing Metal at Home (The LJS method)

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In my free (pah, free) time I do metalworking. Sometimes I make Mini Swords, other times Jewellery. Sometimes I make things that even I don't know what to do with them.
But regardless, they are all silver and shiny.

Seeing as a lot of my recent jewellery has been made from Aluminium, I decided to look at Anodising. After Anodising Aluminium it should be more receptive to paints and dyes.

This instructable will cover the process of Anodising and Dying small Aluminium parts using materials that anyone can find.


Oh, and LJS? Lemon Juice Substitution. I use it as a generic electrolyte for any electrochemical reaction at home.


The Setup:
Small container. Mayonnaise container, jam jar etc.
Aluminium scrap
19V+ power supply going to crocodile clips (May work down to ~12V. Read the next page)
Coke can
Patience

Consumables:
4 Lemons (Or lots of vinegar)
Water
Object to be Anodized (Aluminium)
Dye, ink or paint (I used Parker's Quink, but you can use just about anything though)

 
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Step 1: The Theory

I had heard about Anodizing before, and seen it often enough, so it was natural that when I wanted to colour metal, it would come into my head.
My first step was to gather information. As per my usual on the web, it was Wikipedia first.

Here are the claimed benefits of Anodizing:

"Anodizing increases corrosion resistance and wear resistance, and provides better adhesion for paint primers and glues than does bare metal. Anodic films can also be used for a number of cosmetic effects, either with thick porous coatings that can absorb dyes or with thin transparent coatings that add interference effects to reflected light."
Anodizing - Wikipedia


After wading through the first paragraph or two, I came across good information on the process. It goes something like this:
1) Clean it
2) Put it in an acidic electrolyte.
3) Run a DC voltage through it.
4) Dye/paint it.
5) Seal it

Of course there is a little more involved. I'll go over these in depth in later steps, but here's the overview:
They recommend cleaning it in a solvent bath. I rubbed it with methylated spirits.
They suggest using ... Sulphuric acid. I don't have any, nor do I want any. However, lemon juice is acidic and conducts well enough.
Apparently the process can take anywhere from 1-300 volts, but Wikipedia adds:

"most fall in the range of 15 to 21 V"
Anodizing - Wikipedia

It adds a final piece of advice for us home experimenters:

"Conditions such as electrolyte concentration, acidity, solution temperature, and current must be controlled to allow the formation of a consistent oxide layer. Harder, thicker films tend to be produced by more dilute solutions at lower temperatures with higher voltages and currents."
Anodizing - Wikipedia

Now it was time to go and see just how well it would work.

me10802 months ago
Your cathode has to be more Nobel than your anode(part you are anodizing) look up Nobel chart of metals or galvanic scale. For example: if you are trying to anodize a piece of aluminum and you use a piece of zinc or magnesium for an intended cathode, your anodizing will work in the opposite direction. The further apart the two metals are in the galvanic scale the stronger the effect will be.
Ugifer3 months ago

Interesting 'ible - I may have to try this at some point.

If you are interested in trying other acids, I would suggest starting with citric acid. It's commercially available, cheap (£3 for 500g on e-bay), non-toxic (edible in fact) and is the main acid component of lemon juice so it should be similar to a highly purified version of what you are using now. I'll let you know how it goes if I manage to try this.

Cheers

Ugi

harvie4 months ago

Adding teaspoon (or more) of salt to vinegar will increase it's conductivity.

However i am not sure if anodizing as suggested by this instructable will give you same qualities as more advanced methods... can somebody make comparison based on experiences with the two or electrochemical knowledge?

sdfgeoff (author)  harvie4 months ago

You can use any electrolyte really. I've recently started just using plain salt again, but beware of chlorine fumes.

Anodizing by this method will not be as good as by more advanced methods because ... it's simpler.
For a consistent surface you need the temperature and pressure regulated, you need an even charge distribution as well. This was not taken into account in this ible because I was looking for the simplest possible method to color metal. I was seeking only porosity not durability.

If someone finds a better method though, please tell me!

kmrocks1 year ago
Sorry, great post!
kmrocks1 year ago
You said if anyone knows why one site recommend Lead let me know, so here it goes... Some metals are more active ( Anodic), or more likely to corrode, other metals are less likely to corrode or more noble ( cathode). When you add an electrolyte, metallic path, and a current source, a natural reaction occurs, where the more active ( anode) sacrifices itself to protect the cathode.
jaggdlynx1 year ago
Would it be possible to wrap bare copper wire around the inside of the glass jar to use as the anode? I've seen it done on a larger scale in 5 gallon buckets, but he was using industrial chemicals and it wasn't quite the "can do at home" type of set up. I only ask because I see you mention if the lemon juice turns green it means you have some copper in there somewhere, so I am guessing it's not a god idea with this particular set up (?).
sdfgeoff (author)  jaggdlynx1 year ago
Actually, it will be fine using copper for the cathode. Just make sure that you don't end up copper plating the part (check the polarity of the wires).
Try pickleing vinegar it is much stronger than regular table vinegar, might help...
I would love to see posts about your experimentation with other organic acids.
sdfgeoff (author)  audreyobscura1 year ago
I'll let you know whit I've tried.
I've just added Vinegar to the ible, and plan to try orange juice and some other stuff sometime soon.