Air Cleaner Respray - preparation tips?
Discussion
Hi,
After some advice - I need to repaint my classic car oil bath air cleaner. I have the correct colour engine enamel in a rattle can. I've taken the air cleaner apart into half a dozen large pieces (it's American). They are absolutely filthy (oil and engine grime), but the old paint is non-flaky and complete. What's the best way to get the surface cleaned and sanded? Do I need to remove all the old paint, even if it's a good surface? Obviously it's not bodywork so it doesn't have to be mirror gloss, but I'd like a decent-ish finish.
It's the cleaning and prep I'd really appreciate some advice on please.
Thanks
After some advice - I need to repaint my classic car oil bath air cleaner. I have the correct colour engine enamel in a rattle can. I've taken the air cleaner apart into half a dozen large pieces (it's American). They are absolutely filthy (oil and engine grime), but the old paint is non-flaky and complete. What's the best way to get the surface cleaned and sanded? Do I need to remove all the old paint, even if it's a good surface? Obviously it's not bodywork so it doesn't have to be mirror gloss, but I'd like a decent-ish finish.
It's the cleaning and prep I'd really appreciate some advice on please.
Thanks
Hi, so there are many different elements to this.
The gold standard is to take it back to bare metal, that way you know exactly what the bare surface is like and you can guarantee paint adhesion if you follow the TDS instructions.
I’d get it media blasted, it’s not expensive for small parts like that, any local shot blaster will do that for you. To be fair it’s probably less hassle and probably cheaper to also get them to powder coat it for you at the same time.
If you want to paint it over the old paint you can, but I tell customers that I can’t guarantee my work as I can’t be certain of the new paints adhesion to the old surface. To paint over the old surface you need it to be clean of all the old contaminants so it needs washing and cleaning until you are certain all the oil has been removed, you then need to use panel wipe (IPA) to clean it again. The whole surface then needs scuffing up with 320 grit in every nook and cranny. You can use a red scotchbrite pad which is easier than sandpaper in corners. Then panel wipe it again and again.
The scuffed surface will give the new paint a mechanical adhesion and you could directly enamel over it, but the better way would be to use something like a 2k epoxy primer, this will both seal the old surface to stop any reaction with your enamel and it will also give it a chemical adhesion as well as the mechanical adhesion.
The two key points are cleanliness, finishing with panel wipe, and scuffing the surface enough for adhesion but not so coarsely that the scratch marks will show through the finished paint.
You say you don’t want a show finish but paint won’t stick without either mechanical and/or chemical adhesion, that’s best on bare metal, I would also recommend a decent primer. If you paint over old surface the primer will act as a sealer between old paint and new, meaning you need less of the expansive enamel as it’s only covering the primer, and hopefully preventing any paint reactions.
You can’t prep too much, the whole finish will be based on the effort you put in beforehand.
Let us know how you get on.
The gold standard is to take it back to bare metal, that way you know exactly what the bare surface is like and you can guarantee paint adhesion if you follow the TDS instructions.
I’d get it media blasted, it’s not expensive for small parts like that, any local shot blaster will do that for you. To be fair it’s probably less hassle and probably cheaper to also get them to powder coat it for you at the same time.
If you want to paint it over the old paint you can, but I tell customers that I can’t guarantee my work as I can’t be certain of the new paints adhesion to the old surface. To paint over the old surface you need it to be clean of all the old contaminants so it needs washing and cleaning until you are certain all the oil has been removed, you then need to use panel wipe (IPA) to clean it again. The whole surface then needs scuffing up with 320 grit in every nook and cranny. You can use a red scotchbrite pad which is easier than sandpaper in corners. Then panel wipe it again and again.
The scuffed surface will give the new paint a mechanical adhesion and you could directly enamel over it, but the better way would be to use something like a 2k epoxy primer, this will both seal the old surface to stop any reaction with your enamel and it will also give it a chemical adhesion as well as the mechanical adhesion.
The two key points are cleanliness, finishing with panel wipe, and scuffing the surface enough for adhesion but not so coarsely that the scratch marks will show through the finished paint.
You say you don’t want a show finish but paint won’t stick without either mechanical and/or chemical adhesion, that’s best on bare metal, I would also recommend a decent primer. If you paint over old surface the primer will act as a sealer between old paint and new, meaning you need less of the expansive enamel as it’s only covering the primer, and hopefully preventing any paint reactions.
You can’t prep too much, the whole finish will be based on the effort you put in beforehand.
Let us know how you get on.
DaveF-SkinnysAutos said:
Hi, so there are many different elements to this.
The gold standard is to take it back to bare metal, that way you know exactly what the bare surface is like and you can guarantee paint adhesion if you follow the TDS instructions.
I d get it media blasted, it s not expensive for small parts like that, any local shot blaster will do that for you. To be fair it s probably less hassle and probably cheaper to also get them to powder coat it for you at the same time.
If you want to paint it over the old paint you can, but I tell customers that I can t guarantee my work as I can t be certain of the new paints adhesion to the old surface. To paint over the old surface you need it to be clean of all the old contaminants so it needs washing and cleaning until you are certain all the oil has been removed, you then need to use panel wipe (IPA) to clean it again. The whole surface then needs scuffing up with 320 grit in every nook and cranny. You can use a red scotchbrite pad which is easier than sandpaper in corners. Then panel wipe it again and again.
The scuffed surface will give the new paint a mechanical adhesion and you could directly enamel over it, but the better way would be to use something like a 2k epoxy primer, this will both seal the old surface to stop any reaction with your enamel and it will also give it a chemical adhesion as well as the mechanical adhesion.
The two key points are cleanliness, finishing with panel wipe, and scuffing the surface enough for adhesion but not so coarsely that the scratch marks will show through the finished paint.
You say you don t want a show finish but paint won t stick without either mechanical and/or chemical adhesion, that s best on bare metal, I would also recommend a decent primer. If you paint over old surface the primer will act as a sealer between old paint and new, meaning you need less of the expansive enamel as it s only covering the primer, and hopefully preventing any paint reactions.
You can t prep too much, the whole finish will be based on the effort you put in beforehand.
Let us know how you get on.
Hi really appreciate the time you've taken to reply.The gold standard is to take it back to bare metal, that way you know exactly what the bare surface is like and you can guarantee paint adhesion if you follow the TDS instructions.
I d get it media blasted, it s not expensive for small parts like that, any local shot blaster will do that for you. To be fair it s probably less hassle and probably cheaper to also get them to powder coat it for you at the same time.
If you want to paint it over the old paint you can, but I tell customers that I can t guarantee my work as I can t be certain of the new paints adhesion to the old surface. To paint over the old surface you need it to be clean of all the old contaminants so it needs washing and cleaning until you are certain all the oil has been removed, you then need to use panel wipe (IPA) to clean it again. The whole surface then needs scuffing up with 320 grit in every nook and cranny. You can use a red scotchbrite pad which is easier than sandpaper in corners. Then panel wipe it again and again.
The scuffed surface will give the new paint a mechanical adhesion and you could directly enamel over it, but the better way would be to use something like a 2k epoxy primer, this will both seal the old surface to stop any reaction with your enamel and it will also give it a chemical adhesion as well as the mechanical adhesion.
The two key points are cleanliness, finishing with panel wipe, and scuffing the surface enough for adhesion but not so coarsely that the scratch marks will show through the finished paint.
You say you don t want a show finish but paint won t stick without either mechanical and/or chemical adhesion, that s best on bare metal, I would also recommend a decent primer. If you paint over old surface the primer will act as a sealer between old paint and new, meaning you need less of the expansive enamel as it s only covering the primer, and hopefully preventing any paint reactions.
You can t prep too much, the whole finish will be based on the effort you put in beforehand.
Let us know how you get on.
I've taken your advice and dropped it off at a specialist media blasting service this morning who will then high temp prime it for me to stop any corrosion so that I can prep and paint it properly when I get it home. I can't have it powder coated unfortunately as it's a classic specific colour and has to match the valve covers etc. It would have taken two days at least to rub down by hand and I'd have no guarantee that the surface wouldn't have been contaminated.
Best regards,
Andy
Good decision, for the price of media blasting its value for money compared to the hours of labour needed on these little parts.
When you rattle can it, do lots of fine coats leaving a good flash time between coats, its really easy to get runs when your doing small parts as you end up being too heavy to get it into the corners, so lots of light coats and plenty of flash time between is the secret. It will cover eventually but might take 4-5 coats rather than one heavy one.
When you rattle can it, do lots of fine coats leaving a good flash time between coats, its really easy to get runs when your doing small parts as you end up being too heavy to get it into the corners, so lots of light coats and plenty of flash time between is the secret. It will cover eventually but might take 4-5 coats rather than one heavy one.
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