Paint Problem

[Nuts-about-cars]

I have a problem with a paint job I'm doing, it's a problem i've not really came across before like this, I'm painting the bottom half of a car, and whilst I've came to be quite a proficient painter, I don't understand this one, I put on my first coat of basecoat, thinned 1:1 with 2k thinners, this was going over UPOL S2025 2k Primer surfacer, and I used Dinitrol 445 stonechip under that. My basecoat reacted, but it also seemed to go on very thinly and ran very easily like it was overthinned, which I don't understand as basecoat is normally thinned 1:1, I'am suspicious of the Dinitrol 445 stonechip I used but I'm not sure if this is what caused the problem. Can anyone identify where I went wrong? Each stage was given 24 hours before being rubbed down and taken to the next stage. I've used the upol 2k primer in hundreds of jobs and never once experienced this!

 

[norsa]

Can you elaborate on exactly what the reaction was. Very unlikely to be a substrate issue.
what colour base? Nick.

 

[Nuts-about-cars]

The reaction was it wrinkled, it was a white basecoat I was putting on before putting on a red basecoat then clearing it, the white never got past the first coat. I'm beginning to suspect I had too much thinner in the basecoat, as it was very thin and runny, yet I mixed it 1:1, 200ml total mix, 100ml of basecoat and 100ml thinner. The reason why I was using a white basecoat is because I went to buy a white primer, but the bodyshop supplier didn't have any but suggested that I use white basecoat instead, I wasn't keen on the idea to start with, now I know why! As I said before, the whole system was, Dinitrol 445, UPOL S2025 dark grey 2K primer surfacer, then this white basecoat, which is a make I've never heard of before, General Paints Genrock basecoat, it wasn't a special mix, it was an off the shelf can of basecoat.

 

[steveo3002]

does sound over thinned..cant think why it would run otherwise

didnt leave some thinners in the gun from last time did you?? ive done that lol

 

[langy]

Stonechip normally goes on top of primer, you have put primer on stonechip, although I wouldn't of thought it would do that, also some basecoats thin 2-1

 

[Nuts-about-cars]

So I should put the dinitrol stonechip OVER the primer and then my basecoat? I normally use Gravitex for stonechip and prime and paint over it and never had a problem doing it that way, but I needed a smooth stonechip which is why I didn't use it this time.

 

[Nuts-about-cars]

Probably the 2:1 for this particular basecoat is the most likely scenario for why this happened, the TDS instructions were very vague, it was overthinned. I'm going to buy a proper white primer and not use the white basecoat again, after I've sanded off the wrinkled mess again, I can't decide whether to shoot on a coat of Barcoat or not just in case I've missed something, or just go again, watch how I thin the basecoat, and hope it doesn't react again!

 

[langy]

So I should put the dinitrol stonechip OVER the primer and then my basecoat? I normally use Gravitex for stonechip and prime and paint over it and never had a problem doing it that way, but I needed a smooth stonechip which is why I didn't use it this time.

Thats the way I've always done it although I prefer epoxy primer then stonechip, the epoxy is harder than hi build and gives the topcoats a tougher base to go onto.
I've seen people use celly primer and 2K topcoat and they suffer more stone chipping, its because the primer is softer and allows the topcoat to flex when the stone hits it.

 

[langy]

Probably the 2:1 for this particular basecoat is the most likely scenario for why this happened, the TDS instructions were very vague, it was overthinned. I'm going to buy a proper white primer and not use the white basecoat again, after I've sanded off the wrinkled mess again, I can't decide whether to shoot on a coat of Barcoat or not just in case I've missed something, or just go again, watch how I thin the basecoat, and hope it doesn't react again!

Personally I wouldn't Barcoat it myself, much better to take it back and redo, only my opinion but if the correct mixing ratios are not obvious its generally not a good quality product.
Also did you use basecoat thinner, its a better product for basecoat as the thinner is not so aggressive

 

[Nuts-about-cars]

Ok, thanks for the post, I've taken everything on board, I would agree that the basecoat I used is not good quality, in fact I read the can and it states that it was made in Lebanon! . I'm just tackling the job of cleaning up the mess I made today as it happens, and most of the primer I put on is still intact, just the bits where the runs collected is where it reacted/melted everything underneath, so I'm taking all of those bits back, feather edge it, and I'll take it from there. I've bought a good quality tin of light grey primer and hopefully that should be that!

 

[Nuts-about-cars]

No, I didn't use a specific basecoat thinner, I just used 2k thinner like I always do, but to reduce the possibility of any more aggro, I think I might go back to the paint shop and get a tin the specific thinner like you say, especially as it is less aggressive, as I think probably it was the aggressive solvent that caused this in the first place. To clear up, I don't think it was the Dinitrol stonechip that caused this, I did an experiment on some scrap steel with it and the basecoat, and no reactions! My thoughts on it as I say and most people seem to agree that it was my crappy basecoat overthinned that caused the bother!