F-150 aluminum hood corrosion
- Thread starter Bossed
- Start date
Chris_Hamilton
Trying to be the best me, I can be
Important to note that the type of corrosion is called galvanic corrosion. It happens when aluminum is contaminated with iron/steel. Different than corrosion on steel.
I've done the same as Barry said in the past on a lot of those Fords. I prefer to use 180 instead of 80 as aluminum is softer than steel and you can remove a lot of it with 80 if not careful.
The quick collision way is to use etch primer after sanding. No aluminum prep needed. I've used the PPG SX system as well. If you do it this way if you don't already have some on hand, it's expensive. You can use a phosphoric acid product in place of it. Make sure it's neutralized. Then two coats of epoxy.
Make sure that you use fresh paper. You don't want to use paper that has already been used on steel. You should also take care to have your work area free of any steel residue or remnants as steel contamination is the cause of galvanic corrosion.
I've done the same as Barry said in the past on a lot of those Fords. I prefer to use 180 instead of 80 as aluminum is softer than steel and you can remove a lot of it with 80 if not careful.
The quick collision way is to use etch primer after sanding. No aluminum prep needed. I've used the PPG SX system as well. If you do it this way if you don't already have some on hand, it's expensive. You can use a phosphoric acid product in place of it. Make sure it's neutralized. Then two coats of epoxy.
Make sure that you use fresh paper. You don't want to use paper that has already been used on steel. You should also take care to have your work area free of any steel residue or remnants as steel contamination is the cause of galvanic corrosion.
RenewAP
Promoted Users
I don't know this to be a fact, but I was told that the inner and outer panels were made from slightly different alloys. If that is true, then the problem will go on forever.
Chris_Hamilton
Trying to be the best me, I can be
Interesting. Never heard that before. The story I always heard was that the hoods were installed unpainted and went through the line where there was still spot welding being done on other parts of the truck. No idea if that's true. Probably isn't.
I didn't think two aluminum alloys were dissimilar enough to react that way. I've seen 3003 and 5052 or 6061 together and they don't do that. Interesting if that is true.
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RenewAP
Promoted Users
Since most of the corrosion that I see seems to happen in the same areas that rust happens (wheel arches, tailgate lips, hood fronts) , I think the galvanic corrosion you mentioned is more likely. The initial corrosion lets more moisture and salts get to the now bare aluminum in the same collection areas as any other metal. If it were the different alloys, I think there would be an even amount of corrosion everywhere that the two alloys touched each other.
Chris_Hamilton
Trying to be the best me, I can be
One more thing to keep in mind. Since AL oxidizes so quickly. You need to get primer on the AL as soon as possible. 12 hours is what I consider the limit. Something may look clean but if it has sat bare for any length of time it will have oxidation.