Primer question (Weld thru application and mixed bare/painted metal)

[Bronco Sully]

Couple questions for you guys. Getting ready to spray some primer onto the floor pans and the surrounding areas.

1. What is the best primer to use if I have mixed bare metal (where I wire wheeled areas that had rust) with some areas that have old factory/original paint left (areas with no rust)? Can I use self etching over old paint?

2. I was going to use a copper based weld thru primer only on areas where my new floor pans mate/flange up with the existing metal (basically in between the metal surfaces). Once I finished the plug welds and grinding them down, I was gong to cover the outside metal with non-weld thru primer. Make sense/Correct?

I am not sure if I am going to paint the floors or bed line them yet.

Any advice would be appreciated.

 

[allenfahey]

Couple questions for you guys. Getting ready to spray some primer onto the floor pans and the surrounding areas.

1. What is the best primer to use if I have mixed bare metal (where I wire wheeled areas that had rust) with some areas that have old factory/original paint left (areas with no rust)? Can I use self etching over old paint?

2. I was going to use a copper based weld thru primer only on areas where my new floor pans mate/flange up with the existing metal (basically in between the metal surfaces). Once I finished the plug welds and grinding them down, I was gong to cover the outside metal with non-weld thru primer. Make sense/Correct?

I am not sure if I am going to paint the floors or bed line them yet.

Any advice would be appreciated.

You can either use epoxy primer or etching followed by a 2k primer. Do not use etching under epoxy! Always read the TDS (technical data sheet) which will give you what you can apply the product on, mix ratios, dry times, gun setup, ect.

I personally like using etching and 2K primer because 2K primers sand easier in finer grits. If you choose the etching make sure to only put it on the bare metal. You have to get some on the old paintwork feathered areas and it will be ok if you are carefull. Depending on how good the etching is you can have lifting on the edges. Highly likely to happen if the old paint work is an enamel or lacquer. I would put a couple VERY light coats on and let it flash off anout 10 minutes. Then apply a couple medium coats (let flash between coats) Let the last coat flash off and then apply the 2k primer. It sounds complicated but its really easy.

For the weld thru primer you don't use it for coverage. A very light coat is all that is needed. For the seams you apply primer. After it dries scuff the seams and apply seam sealer. The two part seam sealers are the best but more expensive and requires a special double barrel caulking gun. You can also spray etching, let flash, spray sealer, let flash, caulk, then paint. That is faster than waiting on primer to dry. When I did Ransils floor pans at MEB Wrench and Roast I wound up using 1 1/4 tubes of caulk and did both top and underside of the front floor pans.
If you use bedliner check with them on how they want it. I know if you use Raptor U-POL will tell you to use their primer on bare steel.

 

[Rustytruck]

I used epoxy primer especially when projects sit for periods of time. Properly epoxy primed stuff wont rust even if sitting exposed to weather.

 

[Bronco Sully]

Thanks for the info gents