Originally published October 1996
Disclaimer: The information presented below is believed to be accurate. However, no warranty of any kind accompanies this information.
What is alodining?
Alodining is the chemical application of a protective chromate conversion coating on aluminum.
Why would anyone want to alodine aluminum?
How much alodine solution is required to treat aluminum?
Aircraft Spruce, in their catalog, claims a gallon of alodine solution will treat about 400 square feet of aluminum. The company I bought mine from claimed 80 square feet. I estimate that my RV-6A has between 1600 and 2600 square feet of aluminum surface. (This is the total surface area of all aluminum parts in the whole airplane.) Somewhere between 5 and 30 gallons would be needed.
How large are my tanks?
They measure 5 feet long by 1 foot wide and are filled to a depth of about 2 1/2 feet. This translates to about 94 gallons, or enough to do at least 3 aluminum airplanes like mine. I built the wooden tank structures around custom-made liners of 0.100" black polyethylene. These tanks are big enough to immerse the overwhelming majority of the RV-6A parts, including many skins.
If I were building new tanks today, how large would I make them?
I would make them 5 1/2 feet long by 1 foot wide and about 3 1/2 feet deep. I would fill them to the 3 foot level, or about 125 gallons. They would then accept about half of the parts the current tanks cannot hold. Had I ordered them that size in the first place, the price would probably have been the same.
How much did the tank liners cost, and where did I get them?
The liners cost $250 each plus tax (custom made to my dimensions). I ordered them from a company called Multi Lining and Coating in Bakersfield. Their phone numbers are 800-966-0650 and 805-589-0650. I don't remember the address.
Isn't the large quantity of alodine expensive? Aircraft Spruce gets $17.50 per gallon.
Aircraft Spruce charges a lot for water. I purchased a 10 lb can of Iridite 14-2 powder which, when mixed with water, makes about 128 gallons. This 10 lb can cost $140 in January of 1994. This translates to about $1.09 per gallon. The other tank holds a preconditioning acid solution. Fifteen gallons of the concentrated acid called Isoprep 184, enough for about 100 gallons of solution, cost $112.50. Naturally, tax and freight are extra. I avoided freight charges by picking up the acid and alodine in person at the company plant in Los Angeles. At the time the company was Allied Kelite division of Witco Chemical Corp. Since then, the division was sold to MacDermid, Inc. I have not done business with them. I do not know anything about the current product line, current prices, or even if the Los Angeles plant is still in existence. MacDermid' s phone number is 800-325-4158. The number is probably in Connecticut.
What is the exact process used to alodine a part?
This process sounds horrible. Isn't painting a lot easier?
Well, with a few small parts, I can start at step 1 and do everything up to step 9 in 15 to 20 minutes. I could never set up to paint parts and clean up in that time.
More on Alodining...
Still More on Alodining...
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Revised -- 10 July 1997