Help please (paint)

ElusiveStranger · Posted: Thu May 13, 2010 5:40 pm Post subject: Help please (paint)

As some of you know I've been busy...

I've run into a problem, this is 2k high-build over barcoated areas
I sprayed it on Sunday & within an hour or so I noticed some "rips" forming. These were only 1" or so in length

I got home tonight (4 days after spraying) to see this:

Rear corner

NS rear arch

Any ideas as to why it happened & what the remedy is?

_________________
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Your experiences are worth shed loads to others, including the f'ups - live and learn.
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'78 Bay, 2 litre 091 box, EJ20 NA & the ashtray's on the 'right' side.
I don't lean forward for hills any more Grin

Bugger, missed out on "Live fast, die young"

sven · Jedi Guardian Joined: 27 Dec 2006 Posts: 814

Oh, crap!

You did the painting outside, right? Was it a humid evening?
Humidity increases the stress (surface tension) of the paint when it's curing, paint will always shrink during the hardening and the humidity causes the paint to be brittle during the process. When the surface tension is higher than the mechanical bonding, it will crack.

Probably no problem with the paint. I think it was too cold and too wet outside. Try to respray, thinner layer on a warmer day.

ElusiveStranger · Posted: Thu May 13, 2010 11:34 pm Post subject:

It would have been more of an "oh crap" moment if it had happened *after* I'd top-coated.

Cheers for the reply Sven. It was cold on Sunday & yes I did spray outside (no choice)

I think it's gonna be a sand it back, dust over with less hi-build or even 2k etch.
It really appears to have happened where I'd "spotted" areas first.

I'm just very surprised it's taken around 4 days. The initial splits happened within 1-2 hours and were around 1-2" in length.
_________________
The advice you receive on here is worth the paper it's written on.
Your experiences are worth shed loads to others, including the f'ups - live and learn.
Wouldn't YOU rather learn by someone else's mistakes? So would they.

'78 Bay, 2 litre 091 box, EJ20 NA & the ashtray's on the 'right' side.
I don't lean forward for hills any more Grin

Bugger, missed out on "Live fast, die young"

sven · Jedi Guardian Joined: 27 Dec 2006 Posts: 814

2K clear or paint takes long time to cure if it's not heated. Dry is not the same as cured. When running parts in 60 degrees Celsius they are cured in an hour, but they still "post harden" for a day or two.

ElusiveStranger · Posted: Fri May 14, 2010 8:39 am Post subject:

I just hope it's finished doing its thing.
I'll hit it with a hairdrier when I spray the patches.

It only seems to have happened on the curved sections of my panels, not the long, straight bits.

_________________
The advice you receive on here is worth the paper it's written on.
Your experiences are worth shed loads to others, including the f'ups - live and learn.
Wouldn't YOU rather learn by someone else's mistakes? So would they.

'78 Bay, 2 litre 091 box, EJ20 NA & the ashtray's on the 'right' side.
I don't lean forward for hills any more Grin

Bugger, missed out on "Live fast, die young"

ElusiveStranger · Posted: Sun May 16, 2010 1:29 am Post subject: Update

Sanded the problematic areas down (thanks T2 turbo & Sven)

Snotted on some 2 k etch prime and she's looking like she's good to go.
Hope to put a bit of hi-build back on tomorrow, so I have a primer in all one colour.

Gotta say a big up "up" to all the other people who share "my" drive. I get paranoid when they pass.
So many have commented that I'm doing a cracking job, along with the "is it worth it?" comments Happy

JP/RB you ain't gonna recognise the NS

Anyone got a late bay NS door?
_________________
The advice you receive on here is worth the paper it's written on.
Your experiences are worth shed loads to others, including the f'ups - live and learn.
Wouldn't YOU rather learn by someone else's mistakes? So would they.

'78 Bay, 2 litre 091 box, EJ20 NA & the ashtray's on the 'right' side.
I don't lean forward for hills any more Grin

Bugger, missed out on "Live fast, die young"

ElusiveStranger · Posted: Tue May 25, 2010 7:43 pm Post subject: Update

Well I sanded right back & etch primed, followed by high build

Splashed out on some Java Green, along with a new back box....

I've just finished replacing:
NS Front arch, b-post, sills, top hats, JPs, rear arch (inner & outer) & rear corner
My NS door and tailgate are worse for wear but they looked even worse with fresh paint all down the side so I quickly topcoated over the rust Grin

No, I'm not going to post the runs!

Just gotta sort the back, front, roof...

Steffan, that's my workshop, welding bay & paint booth - the great outdoors
_________________
The advice you receive on here is worth the paper it's written on.
Your experiences are worth shed loads to others, including the f'ups - live and learn.
Wouldn't YOU rather learn by someone else's mistakes? So would they.

'78 Bay, 2 litre 091 box, EJ20 NA & the ashtray's on the 'right' side.
I don't lean forward for hills any more Grin

Bugger, missed out on "Live fast, die young"