Aluminium oxidisation

P

Phoenix

New Member
Guys I need to pick your brains.... what is the best way to get rid of aluminium oxidisation?

One small area of my bonnet is suffering with this and a repair I did has failed to cure the problem hence I have to return to it.

Is the best way to simply grind and clean the area and then prime it??? What primer would you use?

I am thinking of lightly grinding the surface of the bonnet so that it looks clean and then using the trusty Dremmel with a wire brush to make sure the area is free of the dreaded oxidisation. Once clean I wondered if a regular primer would be enough.

What do you all think :?:
 
Not entirely sure what would be the best approach, although I don't think ordinary primer would do the job. Have you looked at the Frost catalogue? There may be something in there that would fit the bill. I've had the same problem with my boot lid, I'm waiting til the summer and I'm going to get the boot lid clear anodised then will spray over the top. I think that would be the most comprehensive way of dealing with it.
 
I've always used a small wire wheel on a power drill or die grinder, very carefully though. If you do that you must be careful not to push too hard, go too fast and put too much heat in the panel, otherwise you're likely to cause damage to the aluminium. I've never had any oxidisation come back after doing that.
 
One thing you need to bare in mind is that aluminium once exposed, oxidises at a much quicker rate than steel, although if I remember correctly the oxidisation will then prevent the aluminium coming into contact with the air, to a degree.

If you start to prep the aluminium, you'd be best getting it done in one run, rather than starting it and leaving it.
 
In a former life when I used to work for the NZ post office (radio division) we used to regularly prep and paint aluminium panels for rack equipment, never did any thing other than the same you would to a steel panel, sand with 180 then down to 400 grit, 2 D primer then top coats. These days when i get various firms to build aluminium enclosures for the power supplies we build they chromate the raw aluminium prior to powder coating, this would now be my prefered method, chromating not only is extremly weather resistant it also helps with paint adhesion (so I am told).

Graeme
 
This is what I do :) I pinched this from elsewhere as I'm a lazy a writer :wink:
This works unless it's where your brace work is on the under side of the skin and it comes from where you can't get to :|

Etch primers for bare metal

Etch Primers
Supplied as primer base plus activator, to be mixed before use. Provides maximum adhesion to bare metal and better corrosion resistance. Absolutely essential for aluminium or galvanized steel. The activator is usually phosphoric acid based, therefore do not store activator or mixed primer in metal tins. The useful life once mixed is about 48hrs.
There are two general types available;
Etch Primer-Fillers have moderate filling properties similar to cellulose primers, and are applied in two or three wet coats, leaving 10 - 20 mins between coats to allow solvent to evaporate.
Suitable for minor filling uses, or can be overcoated with cellulose or 2-pack primers.
Wash Primers, that is, with no filling properties at all, are usually applied as one single wet coat over all bare metal areas.
These are used simply for maximum adhesion and must be overcoated with cellulose, 2-pack or synthetic primer filler to achieve the required build and moisture protection.
If any etch primer is used under a conventional primer filler, then one single wet coat is sufficient The etch coat must be dry (resistant to a light fingernail scratch) before continuing with either primer filler or paint.
Etch primers are sensitive to moisture, so must NOT be left for more than a couple of hours without either primer-filler or paint being applied.
 
At work we use a product called Alodine to treat ally bits prior to priming and painting. Your local tame aircraft Mechanic should be able to scrounge you some from work.
Failing that, try spotblasting it with sodium bicarbonate and a good rinse with hot water then prime it with a good quality primer and paint as soon as possible as primer is not impervious to water contrary to popular opinion.
 
ghce,
You're spot on with the chromating process, I'd forgotten about that. It's been some time since I sent anything to have that done. I've used it on magnesium engine cases before and it works a treat. Leaves a nice surface to paint onto aswell.
 
Steve

I has to be ground right back, filled, etched, primed and then painted. You have to get right in ands get ALL the corrosion out, or else it will come back. The problem being is, is that etch primer applied to local areas, often reacts with other painted surfaces.

If you want it painted, it is preferable to bare metal it, then etch prime it out of the gun. The prime it. The primer is then flatted right back and then the top coats applied. Whilst off the car, the inderside can be treated as this is often corroded and mat blacked out of the gun. Its a big panel and a lot of work. As stated before, we can come to an arrangment over painting the bonnet and other panels should you wish.
 
Somethings just occurred to me Phoenix. I believe you're in the Dagenham region. Iirc there was an issue sometime in the late 80's/early 90's with oxidisation of bonnets,boots and roof panels of cars in that area due to the industrial areas along the estuary (can't mention any names but there is a particularly smelly one) pumping out various types of toxic pollutants into the atmosphere. I seem to remember plenty of scabby Ford's, Vauxhall's and in particular SD1's around that time. Not really sure if it's relevant but it may be worth buying a cover if the vehicle lives outside if there is still filth being pumped into the air around them parts.
All the best.
 
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