Raptor Liner Adhesion Issues (1 Viewer)

[AirheadNut]

Last winter I built a small, off-road trailer and decided on Raptor Liner for a finish based on lots of good reviews and ease of application. The entire steel trailer was sanded with 120-grit paper, then thoroughly cleaned with acetone and a wax and grease remover prior to applying the Raptor epoxy primer. I sprayed the primer with an HVLP gun and let it cure before applying a couple of coats of tintable Raptor with the included spray gun. The coating cured quite hard like I expected it to, but a couple of months later a ~50 mile trip on gravel roads thoroughly chipped the Raptor liner on the leading edges of the fenders and the front of the trailer box. The chips go right through both the Raptor and the primer, exposing bare metal. Also, after transporting a few things in the trailer box large chunks of Raptor liner are chipping up off the floor. At this point I am unsure if this is caused by improper prep or application techniques when I sprayed the trailer or if there are other factors at play. I would also be open to recommendations for how to fix it. Out of curiosity I took the trailer to a local LineX/Rhino Liner shop and they said if I brought it in blasted to bare metal they could coat it for around $2000, which is definitely out of budget.
Here is the trailer prior to paint:

Applying primer:

And after applying the Raptor:

The finished product:

 

[Pitter Patter]

Cool trailer. Honestly I think this is just the limits of the product. There’s a really good YouTube video of all the different undercoating where they do a consistent application then hit them with a shot from a constant velocity. Raptor liner doesn’t fare well. The gummy stuff works best because it observes the impact. I say just touch it up and roll with it.

 

[Splangy]

If it chipped through to the bare metal areas, it’s an adhesion issue between the primer and steel. You may not have actually cut the steel much as you thought with the 120 grit paper.

I’m not familiar with the UPOL epoxy primer so I can’t speak to its performance. Is there an induction time prior to application? Was it followed? Did you thin it with anything? Were the temps of the metal and primer appropriate during application? Was it applied to adequate film thickness? Was the raptor liner also applied to proper thickness?

 

[sunrk]

U-Pol have some special products that seem to be necessary for good bonding of final coating to the substrate surface. I'm still thinking of Raptor coating the roof of my 80 series to sort out the issue of 31 year old non-clear coated factory paint decay, etc. as an experiment.

I don't have access to any enclosed space or a booth. I'd be doing it fully outdoors and probably not with a spray gun.

 

[AgentOrange]

Sounds like a surface prep issue to me. I have my Cruiser Raptor lined, but it was sanded pretty aggressively before I shot it myself. I have used PitBull adhesion promoter before on bare metal on new projects and that has seemed to help. Maybe something similar you could use

 

[AirheadNut]

Thanks for all the input! To answer a couple of questions: I followed all the instructions provided by UPOL for application and curing of both the epoxy primer and the raptor liner. The UPOL website seems to indicate that one can use either their adhesion promoter or epoxy primer. I chose the primer over the adhesion promoter due to the size of the project. Application temperatures were in the 65º-75ºF range.

I think the comments are accurate about surface prep, looking back at photos I don't think the sanding was able to cut through the mill scale on the hot rolled sheet metal, adhesion is better on the tubing that I prepped by removing the scale prior to welding.