How to etch aluminum.


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Old 08-12-00, 05:48 PM
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I have some aluminum trim and want to paint it, I was told to etch it first but don't know what to etch it with,help.
 
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Old 08-14-00, 10:55 PM
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Your question: how to etch aluminium.
Unless the surface is anodized or severly oxidized etching is not necessary. There are safer means to accomplish the same thing.

Frankly, the acids used to etch aluminium are hazardous. They are phosphoric, hydrofluoric, and hydrochloric. The hazardous component is one of concentration, not necessarily the presents of. For example, 'Coke a Cola' contains phosphoric acid and so do many fertilizers.

The least risk to you for removing heavy oxidation or an anodized coating is with 'White Spirts' (Painters Naphtha) [as a lubricant and protective coating] plus wet or dry sandpaper and elbow grease. (Do not use steel wool or scratch pads for the abrasive. Aluminum Oxide sandpaper is a second 'in a pinch choice' for the abrasive).

Very mild oxidation can be removed by powerwashing.

Sometimes a lemon juice or vinegar wash (with scrubbing) followed by a rinse of a very dilute solution of TSP and water is all that's needed to remove oxidation.

The process of acid etching removes metal. If acid etching is absolutely necessary (heavy oxidation or an anodized coating) your first and only choice should be a propriety product. A widely available product is 'Nice n Easy' Aluminum Door & Window Frame Cleaner. DO: read the instructions, and purchase the safety gear at the same time. It contains both phosphoric and hydofluoric acids (diluted, but they should be respected). Some scrubbing with a natural fiber bush may be necessary. Other similar products exist also.

(If you need to know the safe disposal means of excess material [other than taking it to the Fire Department] repost and I will explain the process).

For very heavy oxidation or a tough to remove anodized coating the safest thing to do is to hire it done. Attempting to make or use a stronger concoction is not the thing to do, especially when you don't understand the basic process.

Rub a cut lemon on the surface, then wipe it dry. If an improvement occurred, you're dealing with oxidation. Otherwise it's an anodized coating or another protective
coating.

 
 

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