Using anodised aluminium in a brass housing
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Re: Using anodised aluminium in a brass housing
Re: Using anodised aluminium in a brass housing -- neilj	Post Reply	Top of thread	Forum

Posted by: kelly_bramble ® 12/15/2005, 08:19:56 Author Profile Mail author Edit

Look on the following page for galvanic compatibility information - /galvanic_capatability.htm. Chances are, you should be fine. Particularly when the assembly is surrounded by diesel. The anodized surface, if not damaged, should provided very good oxidation control during storage.

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Re: Using anodised aluminium in a brass housing
Re: Re: Using anodised aluminium in a brass housing -- kelly_bramble	Post Reply	Top of thread	Forum

Posted by: neilj ® 12/15/2005, 09:36:26 Author Profile Mail author Edit

Thanks for the reply. The web link you sent me covers Corrosion and Galvanic Compatability of metals. It states that for normal environments there should be not be difference more than 0.25 V between the metals. Brass and Aluminium on that basis give anything between 0.35 V and 0.55 V depending on which alloy of Al. is used. My Al. shaft is anodised though, so does this mean that the galvanic compatability should be measured between anodised surface (Aluminium Oxide) and brass and not aluminium and brass?

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Re: Using anodized aluminium in a brass housing
Re: Re: Using anodised aluminium in a brass housing -- neilj	Post Reply	Top of thread	Forum

Posted by: kelly_bramble ® 12/15/2005, 10:49:11 Author Profile Mail author Edit

Actually, aluminum oxide is grown out of the surface during anodizing and then becomes aluminum hydrate that is extremely hard. Because the anodized surface is extremely porous the aluminum hydrate can be easily dyed. The dye helps to seal the base aluminum from oxygen, thus corrosion. Because the aluminum hydrate forms from the aluminum oxide, you already have a corrosion resistant surface coating ( you cannot rust ~ rust ).

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