RBrid

Hi there. I want to prep the windshield frame of my '77 for primer. It only has little surface rust at the bottom corners & looks great otherwise.

Do I need to get to the bare steel all around, inside and out, or can I just sand the frame smooth and leave some of the existing paint?

I'll use an epoxy primer that's appropriate for the urethane that is going to be applied on it.
I'll check with SPI if their black epoxy primer is OK - and get something else if not.

Thanks for your input.

Medfordautobody

You can buy primer specifically for windshield adhesive. I always use it, better safe than sorry. I would say go to bare metal as much as possible. leave the bare metal and use windshield primer directly over that (use half inch tape to mask a bead around the perimeter of the frame where the adhesive is gloing then prime over it and remove the masking after primer is dried). Most pro glass installers get a bit pissy if you paint over the pinch weld areas where they are going to be working. They always prefer their primer to go directly over bare metal when possible.

DUB

100%

To explain WHY glass installation companies get 'pissy' is because of possible shear.

In your photos I can see multiple layers of product on the windshield frame where the urethane goes. THESE layers is where todays current standards NO LONGER prime and paint this area. Because the paint and primer SHEARING between the layers in an accident. SO.,..that is WHY...less is MO BETTER. The areas where the urethane does not go can stay unless you have rust and wan to deal with that.

Epoxy priming the frame where the adhesive is NOT going is fine just like how Medford mentioned if you choose to strip everything off of it.

I have used epoxy primer( not SPI) on the area where the urethane goes and it does fine...BUT I am NOT applying a lot of primer and this us usually due to really bad rust pitting. BUT if the steel is good....I let my glass guys do what they can warranty. For the glass company...if it is a big company....they are worried about liability because most cars today use the glass that is bonded to a panel as an actual part of structure. I know your Corvette does not fall into that scenario...but the glass companies usually do not care and have to make sure it is bonded in correctly.

DUB

RBrid

This is all good info Medford and DUB, thank you! If you know a good black primer for windshield adhesive and feel comfortable about sharing with us, please go ahead.

If I decide to install the windshield myself, it's better to put the urethane on a thin coat of that special primer instead of bare metal, right? Just want to make sure I do the best thing.
(I might not find a windshield installer I can trust enough for my vintage baby)

DUB

For an epoxy primer I would use PPG's DP 90LF....for the areas WHERE the urethane is NOT being applied.

The reason I use it in some cases is because I know what I am doing with it and I do not get an excessive film build when I do use it. Unless you know what you are doing when you apply the epoxy primer....then do it....its your car.

As for you installing the windshield yourself...that is doable. AND the urethane CAN NOT......REPEAT...CAN NOT be applied to bare steel. The urethane windshield adhesive MUST be applied to the APPROVED primer that the manufacturer of the urethane that YOU plan on using dictates.

DUB

RBrid

Ah, that clears things up for me! Thanks again DUB.

DUB

Just trying to help...this is important and should not be taken lightly.

DUB

crazywelder

But I go a step further on all on window frames and steel bodies. I use an acid wash over the bare metal followed by DPLF. Then I tape off the DPLF in the window channel area throughout the body prep, color and buff stages to avoid any additional paint build up or contamination in the window channels. I use PPG 579 metal cleaner (acid) followed by PPG 520 metal conditioner (zinc coating). DPLF is compatible with these products. SPI epoxy is not compatible with any metal prep acids or zinc coatings.

DUB

I agree with using an approved acid etch product so the epoxy primer can have better 'BITE'. And I am glad you mentioned it....because I do use conversion coatings when I am concerned about MAXIMUM ADHESION.

AS I wrote before.....I ALWAYS recommend that IF a person is going to be installing a windshield..>CALL the manufacturer of the urethane and talk with them on what they want you to do. REGARDLESS of what has been mentioned in these posts.

In most cases of bad/pitted rust....I will sandblast the rusted areas on a windshield frame and not use an acid etch.....depending on how bad the pitting is. YES...the acid etch is GREAT...but if the surface is not the best and I feel that the acid can not be able to be controlled and thoroughly removed as designed...I will not use it. I do not want to introduce an acid that can get into an area and stay there and not be able to be removed....and thus cause for another possible problem.

If this post starts to head down the road to prepping metal parts correctly....it might make some peoples heads spin.

DUB

RBrid

Very cool crazywelder. I started to read about PPG DX 579 Metal Cleaner and PPG DX 520 Metal Conditioner. Good to know about these products, as well as the PPG DP 90LF. Thanks.

The SPI epoxy primer cannot be used on top of a rust converter either.