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Small Bubbles Appearing After Respray


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#1 minimowta

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Posted 12 January 2020 - 04:28 PM

Hi All,

I'm looking for a bit of advice please.  Just over four years ago my MY2000 MPI had a new front end (but we kept the original bonnet) and sills fitted and was resprayed except for roof and rear between the seams.  All seemed well until last summer (3.5 years after the work was done) when I noticed small bubbles appearing down either side of the bonnet.  I thought it was rust but the bubbles we not "rust" shaped, rather more regular, looking like drops of water.  Over the last 6-9 months things have got worse and all the other panels that were resprayed have much smaller bubbles appearing - it looks like the car has got goosebumps!!  I'm hoping to upload some pictures in a minute. They're taken of the rear corner of the bonnet on the offside.

 

Attached File  P1120948 (2).JPG   58.58K   1 downloads

Attached File  P1120951 (2).JPG   36.09K   1 downloads

 

I took the car back to the bodyshop that did the work and he said he had never seen it before and said the work was done 4 years ago and there is nothing he can do!!  He asked if someone had been grinding near it - no and it isn't that sort of rust spot induced by a steel filings anyway.  It seems to be coming from inside.

 

Only the panels resprayed are effected but not all over.  Some panels have a patch but another part of the panel is clear..... still to breakout I suppose!!

 

The car lives outside and occasionally has a cover over it - one of those Stormforce breathable jobbies from minispares.

 

Any help, advice, experiences would be great, thank you.

 

Cheers,

Mike 



#2 sonikk4

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Posted 12 January 2020 - 04:32 PM

Moisture in the paint or primer coat has caused that when it was applied.

 

Sometimes it can appear really quickly or as you have found out sometime later.

 

The biggest issue now is that lot will need to be sanded back to bare metal and the affected panels resprayed again.



#3 DeadSquare

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Posted 12 January 2020 - 04:35 PM

If the bodyshop spray man has never seen that before, he should have gone to "Specsavers" years ago.

 

That is rust bleeding through because of poor preparation.



#4 sonikk4

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Posted 12 January 2020 - 04:38 PM

If the bodyshop spray man has never seen that before, he should have gone to "Specsavers" years ago.

 

That is rust bleeding through because of poor preparation.

 

Going to disagree with you there.

 

I sprayed my wifes mini in celly using a 3hp 50ltr compressor many many years ago. The water trap was not the best. The paint looked ok but after six months the whole car looked like that. And no it was not rust. All new front end etc. No rust.



#5 absx2

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Posted 12 January 2020 - 05:57 PM

Yep, the dreaded micro blisters. A bare metal respray is the only fix.

Too late now but anyone with a resprayed car should avoid car covers at all costs as it draws them out.

Frost and cold weather do the same and sometimes they almost go away in hot weather. 



#6 dyshipfakta

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Posted 12 January 2020 - 09:23 PM

Moisture on the panels or in the air when the paint has been put down. Needs starting again

#7 Homersimpson

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Posted 12 January 2020 - 10:46 PM

As above this is micro blistering and may be due to keeping the car under a cover, any cover which touches the car is not a good idea as it can cause this by trapping moisture between the car and the cover which then finds its way into the paint. 

 

A bare metal respray is the only cure if you can't live with it as it is.



#8 sonscar

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Posted 13 January 2020 - 11:19 AM

Ironically the paint on my inherited Mini has been ok whilst it lived outside,but has microblistered whilst it has been in the garage being worked on.Steve..



#9 Shep76S

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Posted 13 January 2020 - 04:07 PM

Never seen it on steel cars, on glass fibre cars it is more common.

#10 minimowta

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Posted 24 January 2020 - 08:46 AM

Thanks for all the replies.

 

The original bodyshop doesn't want to know so I've been to a couple of others.  At around £2.5k it's more than the car is worth!!  We're going to have to live with it.

I'm intrigued as to why it took so long for the bubbles to appear if anyone could help please.

 

The cover was only ever put on when the car was dry and was regularly removed to drive.  We only used the cover to keep the bird droppings off because they would eat into the paintwork if left on - even for just a few hours!!  I know its corrosive stuff but I've never known it to eat into paint so quick!!  Maybe there was something wrong with the paint making it porous - only the resprayed panels are experiencing these bubbles.  Again, any help and advise would be much appreciated.

 

Cheers,

Mike  



#11 bluedragon

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Posted 24 January 2020 - 10:01 AM

If there was moisture in the paint or primer coats, there's no set time limit for when it works its way out, resulting in blistering. Sounds like the paint job might have been celluose if bird droppings scarred it so quickly? Two pack is much more resistant, especially if it's a urethane or especially a polyurethane.

 

Anyway, since it's coming from below, unfortunately there is nothing you can do that I can think of, other than strip and repaint as others have advised. You can't get to the moisture laden layers, and even if you could, all you can do is remove them - in other words, strip and repaint. Sorry to hear that it's gone bad. Read this for more information. https://www.hmgpaint...-and-prevention

 

 

Dave



#12 spraybeater

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Posted 24 January 2020 - 10:27 AM

I agree with the above and the link provided makes sense! the other possible cause used to be called primmer popping.

If I remember correctly there were some primers that were bad for it although a number of years ago Ault and Wiborg 

grey primmer was particularly bad, I have also seen and repainted a couple of Denim Blue Allegros as warranty jobs

back in the day for a local dealer, that were covered in micro blisters they were vinyl roofed models so bottom half

resprays. I did do some paint work to a Mini recently that had same micro blistering along one side it had been previously

been repaired I do suspect poor prep was the cause.

I spent 50+ years in the body repair trade so have seen and repaired all sorts. :lol:



#13 bluedragon

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Posted 24 January 2020 - 11:23 AM

Yes indeed. In the days when many primers were celluose-based, if the primer used a reducer that was too slow for the temperature (slow evaporation rate) or the topcoat was applied too soon after primer application, that would also cause primer popping as the reducer tried to work its way out of the primer - through the topcoat.

 

As so many have said, it's all in the preparation.

 

 

 

Dave






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