Anodizing Striping 101

[East Coast Ano]

Due to the overwhelming amount of inaccurate, wrong, and just pure misleading information I have come across in the past few years on the topic of striping and anodizing. I have decided to make a post to hopefully put an end to some of the confusion.

I would like to start by detailing the correct means of striping an annealed layer from aluminum parts.

I always start first with a good rinse in warm water. this is to remove any loose dirt particles, I also use this as a chance to get familiar with the parts I am going to be working, to make sure that there are no major chips dings scratches or anything out of the ordinary.

From there I dry the parts and give them a quick scrub with "toluene C7 H8" an extremely powerful and toxic solvent. This step will in essence remove anything that is on the gun from adhesive left behind from old stickers, to the gun oil that I commonly used in Mags. The toluene dries almost instantly so there is no need to blow or wipe the parts dry.

The parts should now be loosely racked. I do this by twisting an aluminum wire thru any hole or opening of the gun. This is not going to be a permanent means of racking the part and it is un-racked after the part has been thru the de smut process so that it can be polished or bead blasted.

I then soak the parts for around 5 minutes in a bath of degreaser that is heated to 80C degrees. I use an industrial degreaser that is non caustic. I buy it in 50lb pails and mix it 1lb: 1gal. There are a wide range of companies that make equivalent products and I have a friend in the northern part of New Jersey that swears by Dawn dish soap. You may wish to use a soft bristle scrub brush by hand or a circulation pump in the tank for some agitation but it is really not necessary.

Following the degreasing, give the parts a quick rinse in fresh water.

I would like to add at this point. During all of the steps listed above there is no permanent damage that could be caused to the parts. From this point onward any mistakes you make could render your parts useless.

That being said, the nest step is the actual striping of the parts takes place. The cleaned parts are then suspended in a bath of Deionized water and “Sodium Hydroxide NaOH”. The bath should be heated to around 85C degrees prior to introducing the parts. The solution will react with the aluminum in this reaction tiny air bubbles will form along the surface of the parts. This can lead to problems with the surface no striping in an even fashion The use of a circulation pump should be used to keep the solution flowing and prevent bubbles from adhering to the parts. Depending on the thickness of the annealed layer that is being striped and the grade of aluminum that the parts are made of the use of agitation might be recommended. A medium bristle brush should be used to avoid leaving scratches on the parts. After the parts have been striped in many cases you will notice a black sort of film on the parts this is typical and is addressed in the de-smutting step that comes next. time needed will depend on many features including the bath temperature, ratio of water to Sodium Hydroxide, the amount of agitation if any that is present, the type and or grade of aluminum, and the thickness of the annealed layer that is being striped.
Rinse the parts well in clean deionized water.
The now striped parts will appear dirty; this is referred to as smutting. To remove this from the parts we use a quick dip in a mixture of Deionized water, sulfuric acid, and Ferric acid I mix this myself in the shop to around 10%Acid or less. You can also buy de-smut in a concentrated liquid form that is simply mixed with water to the manufactures specs; I find the pre mixed formula to not work as efficiently. This mixture is heated slightly to 55C degrees and the parts should not require more than 5 minutes in this tank. This solution will also remove any metals other then aluminum from the surface of the parts and is commonly used on parts directly before going into the anodizing tank.
After another quick rinse in clean water the parts are finished you can now move on to buffing or sandblasting.


Well now that you know how the process goes let me try and clear up a few things.
A part that has been striped will anodize, color, and look exactly the same as a part that is being anodized for the first time. Throughout the striping and re-anodizing process the overall size of the part will change slightly. This overall change has almost no effect on an automag due to their high tolerances, except for the valve structure.
There has been a lot of concern about the effects of striping on barrels. When done in the manner outlined above and with the added step of running a flexible honing tool down the barrel after polishing and before anodizing. There is a slight change to the bore size I would figure it to be an increase of no more then 0.002 - .004 I will attempt to measure this and update with any finding after the next barrel I do. I as well as many others have had no luck with measuring for the growth of a part with a caliper; the most accurate means I know of accounting for part growth is by using a 720 calculator. The 720 Rule is: 720=ASF x minutes / mils. Where; ASF is Amps per square foot, mils is the desired coating thickness (1 mil = 0.001").

Ok I am getting rather late an I am having a hard time thinking so I am going to review over this when I can find time hopefully in the next day or two and make any required tweaks’. I will also be adding some photos as I find the time to snap pictures while striping parts. I sent of 2 pieces of aluminum with a friend I have that works in a lab he is going to take some pictures on the microscope he works with for me comparing the polished mill finish piece of aluminum to a striped and polished part. If I missed anything major or anyone has any other related questions by all means please post them up on here. If an admin would like this thread moved to a different section I apologize and please do so.

Carl

[East Coast Ano]

saved for pics

[mpsd]

Nice! Thanks for posting this up. Only thing is that maybe it'd be better suited at the Tech Forum, instead of the general paintball chating. And maybe a mod could stick it to the top too.

[Rudz]

And here I thought that spraying parts with Easy Off, and polishing with a dremel was proper annodizing stripping technique

Thanks for the post Carl

[Ando]

Here Rudz...I'll let you borrow my shield

[Daze]

I'm normally not a grammar nazi, but in this case it does bear clarifying that you mean 'stripping' and not 'striping'.

Just so someone doesn't try to zebra their marker and e-rage all over you.

[aerosaaber]

I came in here thinking it was gonna be a how to on making really sweet tiger stripe patterns.
*disappointed*