A bit of advise about seamsealer underbody protection??

[maybachman]

Hi all
Summoned up the courage to remove the cover on the Porsche stalled project yesterday for the first time in 8 months. I have been doing some corrosion removal on the underside of the car and ground out surface rust and treated the bare metal with Bilt hamber treatment. Then i etch primed the area and coated in seam sealer to give a bit of thickness to the protection. I then brushed on some cellulose paint unthinned. Some of these areas have cracked.....so do i have to re do the areas or can i just cover with Gravitex and repaint???

Thanks all!!

Geoff

[shin2chin]

If it's cracked it's just that the seamsealer wasn't fully cured before it was painted. If its getting stonechipped over the top I would say it would be fine.

[ejenner]

I would have started with the etch primer. The etch primer is designed to eat into bare metal. Applying it over the top of anything else is silly.

There's also not much point bothering with cellulose paint on a car any more. It's so weak compared with other coatings. It's ok as a colour coat if then putting 2k clear coat over the top. But if we're talking about an underseal situation there wouldn't be any colour right?

[ejenner]

Yeah, so etch primer, then seam sealer. Then normal primer or a colour coat. Then a hard underseal. Then a soft underseal.

[maybachman]

Dec 31, 2014 15:07:17 GMT shin2chin said:

If it's cracked it's just that the seamsealer wasn't fully cured before it was painted. If its getting stonechipped over the top I would say it would be fine.

Thanks for this shin2chin... i need to have a better look when its warmer....cars outside and cant do any paintwork in these temps:(

[maybachman]

Jan 1, 2015 14:05:24 GMT ejenner said:

I would have started with the etch primer. The etch primer is designed to eat into bare metal. Applying it over the top of anything else is silly.

There's also not much point bothering with cellulose paint on a car any more. It's so weak compared with other coatings. It's ok as a colour coat if then putting 2k clear coat over the top. But if we're talking about an underseal situation there wouldn't be any colour right?

Hi ejenner...thanks for the comment. Not sure of your comment regarding starting with the etch primer and putting it over the top of anything else is silly.....the surface corrosion was removed and the area was treated with Bilt Hamber rust converter and then after drying was sprayed with etch primer. Should i have put the rust converter on after the etch primer? I then applied seam sealer and paint. As i am using overpaintable seam sealer and Gravitex is overpaintable i have painted the wheel arches and the underside of the car....should i have not done this?

Regards

Geoff

[ferny]

Etch primer should go over clean metal as it makes a chemical bond with it. It should be left at least 24 hours before painting as it eats into the surface of the metal. Putting it over anything has the potential to stop this from happening.

[maybachman]

Jan 7, 2015 10:32:43 GMT ferny said:

Etch primer should go over clean metal as it makes a chemical bond with it. It should be left at least 24 hours before painting as it eats into the surface of the metal. Putting it over anything has the potential to stop this from happening.

so what should i use over Rust converter?

[maybachman]

Jan 7, 2015 10:32:43 GMT ferny said:

Etch primer should go over clean metal as it makes a chemical bond with it. It should be left at least 24 hours before painting as it eats into the surface of the metal. Putting it over anything has the potential to stop this from happening.

so what should i use over Rust converter?

[taurus]

I use Bonda primer, it's a high zinc coating and goes over rust treatment well.