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Aluminium "rusty" bits


v8bertha
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More metallugy questions...

Where the roofrack sits in the gutters on the Camel the paint has become chipped in places and this is turn has caused moisture :ph34r: to get under the paintwork and make the Aluminium corrode. It's gone powdery in places which I believe is some sort of electrolytic reaction between 2 different metals? :unsure:

If this was steel work, I wouldn't worry too much, I'd just stick some "Kurust" on it, paint it and forget about it, but it ain't steel...

So what is the best was to stop the corrosion from spreading? Is there a magic ally rust cure product on the market that works? Or should I just rub it down and paint over it in th ehope that it won't get much worse?

Any helpful suggestions appreciated!

Dan :D

rustyroof.jpg

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If the roof rack is steel and it gets into contact/close to alluminium, then there is a process called electrolytic corrosion, which makes the white powder. Alluminium will do this anyway over a period of time, but not as quickly.

Les.

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Its electrolytic/ galvanic corrosion..

Aluminium and steel are at different ends of the galvanic series, the ally will act as a sacrificial anode and rot away.

as the others have said, sand it off, etch prime it and top coat it.

the only way to avoid it is to insulate the two metals from each other, so there is no electrical path between the two...

if you google galvanic corrosion i'm sure it'll tell you all you need to know.....

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Its electrolytic/ galvanic corrosion..

Aluminium and steel are at different ends of the galvanic series, the ally will act as a sacrificial anode and rot away.

as the others have said, sand it off, etch prime it and top coat it.

the only way to avoid it is to insulate the two metals from each other, so there is no electrical path between the two...

if you google galvanic corrosion i'm sure it'll tell you all you need to know.....

ARGHHHHHH!!! Scary!! :blink:

I googled, I read...

And I understood!! :blink::o

The electrolyte (in this case water?) provides a means for the ions to move from the anode to the cathode (can't remember which way round, but one is a positive, the other a negative?) That kinda makes sense in my funny world :D

Thanks chaps... Is etch primer available from Halfrauds?

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How we treat alloy corrosion on aircraft

1. remove all loose paint/corrosion back to clean bare material

2. treat cleaned area with a deoxidising solution Deoxidine

3. wipe area dry & coat with etch primer [Alochromate - water based, mixed 20% alochromate to 80% water] for 20 minutes until surface turns a light golden colour

4. wipe of excess with a water dampened clean cloth & dry area with dry non-fluffy cloth

5. apply coat of epoxy primer

6. apply final surface paint finish

hth :D

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