Painting over a patchy chassis

[Chris71]

While I've got the engine out the Chimaera I'm planning to touch up the chassis rails. There were a few areas where the paint/coating was starting to flake, so I've scraped those off. As a result I'm down to the bare metal in small patches, with the old paint remaining where it was sound. Do I now:

a) Use emery paper to blend between the two surfaces and then apply a coat of primer to the whole lot (metal and existing paint), followed by a top coat.

b) Apply primer only to the bare patches, wait 'till it dries, then emery it down before applying a top coat over the whole lot.

c) Try and strip the whole damn lot down to bare metal. I know this is what you'd do in an ideal situation, but I'm really trying to avoid this as most of the existing paint is sound, plus the body is still on and the car is on the ground, so access is very tricky.

[littleredrooster]

Body off, sand blast, powder coat.

Easy.

[.Adam.]

Try POR15, think it's available from Frosts.

[Chris71]

littleredrooster said:

Body off, sand blast, powder coat.

Easy.

I wish.

Sadly that's a little beyond the scope of my brief spot of preventative maintenance. I'm also not convinced its necessary. The paint, on the whole, is good, I think it's just where somebody's used some low temperature paint near the exhaust manifolds that it's had problems.

.Adam. said:

Try POR15, think it's available from Frosts.

Had been considering POR15 - that or Hammerite. Would that be okay to apply to both the pacthes bare metal and the existing undercoat, though? I was a bit worried it might not like the mixture of surfaces.

[steveo3002]

por15 is good on sandblasted metal , will peel off over exsisting paint

look into epoxymastic or jotamasic , those go over preped paint /metal and arent so fussy as por

[tr7v8]

Hammerite is crap for chassis as it is very brittle & will chip off. I'd rub it down aggressively to give a key, wire brush in lecky drill if needed & then use a rust killer if any left, then cold zinc spray & use either rustoleum combi or a decent oil based gloss.

[.Adam.]

steveo3002 said:

por15 is good on sandblasted metal , will peel off over exsisting paint

look into epoxymastic or jotamasic , those go over preped paint /metal and arent so fussy as por

Doesn't the Prep & Ready from the POR15 people prevent this?

[steveo3002]

.Adam. said:

Doesn't the Prep & Ready from the POR15 people prevent this?

it works on rough bare metal only in my experience , so either blasted or rusted stuff cleaned up with their prep gear , the op wants to put it over some exsisting paint and id be 99% sure it will fail

when its good its good , but get it wrong and its poop