gccch

I am a beginner doing my first frame off. Had the frame sandblasted then applied SEM self etching primer. It has been in the garage since May in this condition while I learned how to weld in replacement pieces where there was rust in the frame. It look a long time due to many distractions.

Now I have the repairs done, I am finding some areas that did not get completely cleaned during sandblasting need to be redone. I am questioning the choice of self etch primer as first coating.

Some have since told me I should have used epoxy primer over bare metal. SEM says self etching is also for bare metal to promote adhesion. They say next I should go to a Urethane primer.

Most of the frame is clean, ready for the next step. I have a few areas I want to do over to be sure the rust is completely removed.

The car will see limited use, as a fair weather occasional driver.

Am I ok to proceed with Urethane primer then top coat chassis black? Or was my first choice way off and will haunt me forever? Is this a do over with epoxy primer over bare metal then final top coat?

I do not have the best facility for painting. I have a nice garage that is over crowded - but short term eviction of the wife's car and motorcycles is possible. I can also break into the home heating system for short term heat as it is now too cold outside to paint. But this is my first time....

Thanks,
Greg

DUB

For whatever it is worth. Because I do it rarely due to costs. For me it is cost effective for my customers to send out a frame along with numerous other parts and have it powder coated.

SO...I, myself would use the POR-15 system in this scenario and use it. Which is why is it too time consuming for me to do a frame and charge my customer when powder coating is right at the same price when the smoke clears. I have done it...but prefer to send the frame out.

I know POR-15 can go directly on sandblasted steel...and requires no other prep to the steel. If going over rust and non-sandblasted steel...there is a process of thoroughly cleaning the steel and then applying an acid etch that they offer so when it is washed off and dried....then....you can apply the POR-15 with a spray gun or by using a roller/brush.

You might want to 'fall back' and look at this option. If you are set on spraying a lot of materials...that is up to you. but either way....the surface has to be cleaned so whatever you plan on applying will adhere.

I am concerned about how long the SEM etch primer has been on there. Etch primers usually do not have an unlimited time window. So...this means a topcoat needs to go on it within a specific amount of time. Past that time window...it may need to be re-applied ( or something else)....and usually etch primers do not like to be 'stacked'....and getting the film build too thick. That is not what they are designed for. You might need to call SEM and explain your situation to them.

DUB

gccch

Thanks DUB. As always, good sensible advice. I spoke to SEM and they say I have no issue as long as the self etching primer is still in good shape. I described how the frame has been stored and so there is no issue there. They say the Urethane primer may need to be applied to a roughed up surface, so I may need to do some sanding before I apply that. They also say I can spot clean those areas where the rust was not completely removed and re-apply there, but should be sure to go to bare metal (obviously as that is the intent).

I sure hope the combination of self etching primer and Urethane primer will be a good solution for this old frame. I would hate to see rust re-appearing later.

DUB

Wouldn't we all. RUST....it can be some relentless stuff. It can be stopped...so they always is hope.

Hope all goes well in your project.

Also it seems a bit odd to me why SEM wants the surface roughed up...when the etch primer is what is offering the chemical adhesion and NOT relying on a mechanical adhesion to make the primer stick and adhere. A bit strange. Because roughing up the etch primer and expose bare steel and will remove it and if the urethane primer does not have excellent rust prevention additives in it...I wonder if it will fail.

If their products are compatible with each other...it seems a bit odd that they want the surface roughed up when chemically they should link up.

DUB

gccch

Maybe I was unclear.... SEM said to check with the urethane primer manufacturer if THEY may require the surface to be scuffed up, and to be careful not to go through it as the SEM is a thin coating. That was part of the answer to whether I had a time limit to applying the next product. They said no time limit, but check with the mfr. if it needs to be scuffed.

The other thing is that the SEM etching primer is not expected to stop rust, but the final top coat is expected to seal out moisture....

DUB

This SEM etching primer is more than likely black and in a an aerosol can....correct?????

DUB

gccch

No, it is gray and comes by the quart. I used a preval to shoot it. I have since acquired a spray gun. Here is the product info.
http://www.semproducts.com/aerospace...etching-primer

DUB

In answering some of your question in your original post.

All I will write is that I would not have used the SEM product on the frame. i use this product ( black etch primer)...but it is on small parts that are easily stripped and repainted if needed.

I do not know if you are OK or not. It will all up to the urethane primer company and what they feel....in regards to adhesion to the etch primer and what it will take to prep it for their product.

DUB

gccch

SEM tech line tells me I can use their HS Urethane primer and I should lightly scuff the self etch primer first with a scuff pad. Also they recommended to make the first layer very light. I guess I will go that route rather than restart the process.

DUB

Sounds like a plan.

DUB

gccch

I have the urethane primer on two coats covered pretty well. Now I am preparing for the finish coat of black. I picked up some john Deere blitz black and will try one piece from the rattle can before going ahead with the spray gun.

First, I understand I need to sand the primer with 400 grit. I am in the middle of that now. This is for adhesion, not for making the frame look pretty. There are so many nooks and crannies to get into, plus all the weld splatter, so it is critical to get every square millimeter of surface area for adhesion? Or is this more a quick scuff? If I try to get every low spot I go through the premier on some high spots...

gccch

One other thing... Is a tack cloth ok to remove all the dust from sanding the premier?

DUB

YES a tack rag can be used in conjunction air to blow off and tack your frame.

A RED scotch-brite pad can help also.

I hate it for you...which is why I wrote what I did several posts ago. IF I HAD TO paint a frame...it would all go 'wet-on-wet' so I would not have to prep it between coats.

Do the best you can...and all you can do is hope for the best.

DUB

gccch

thanks DUB. I managed to get my finish coat on today. It went very well after all the concerns and mis-steps. Hopefully the finish will hold up. I am happy with the way it looks today. I finally get to begin re-assembly. Your advice along the way has been invaluable.

Greg

DUB

Greg,
Glad to read that you go it on and it looks good to you.

I am fairly confident that the finish will hold up...especially all the steps and conscience effort to get it prepped correctly that you applied to it....and that is what matters most.

Re-assembling is FUN...I always enjoy seeing it coming back together.

DUB

general ike

"Hunt" thanks for the compliment!!! I am not sure if the spring is heavy duty or not, it was replaced by the PO. In doing so I beleive they also cracked the differential cover which is a later replacement. As far as I understand and I may be wrong but the later diff covers had a wider base for a wider spring by 1/4 of an inch, so if you use a earlier spring the width requires the spacers. It does ride well so it might be a upgrade..

Yes you cannot do as a thorough job with the body on and yes having a lift will save your back, shoulders mind etc. But certainly you can make do with what you have and take your time.

I lifted the car with jack stands and and raised it even further with wood blocks. I then always used a heavy duty jack as a safety measure. it was a pain but it was also my therapy ( I am not sure why!!!) I took me two winters working about one weekend a month. The car was not going anywhere during the winter up North anyway.

Mostly done except I will be going back under next winter to clean up some items I painted under the front suspension that I should have left in the raw and the rear part of the diff did not get power washed well enough so I could not finish it. The car is ready for the summer so it will need to wait!!

Enjoy the summer, Fastimes and get to work in the winter!!! Do as much or as little as you want. Ike

rosslato

I did my Frame and Engine Bay and Rear Underside by jacking it up and laying on my back and wire wheeling and sanding it the hard way. Also took all the parts off and sandblasted them and Por15’d them before top coating. I did this 14 yrs ago and approx 30,000mi later and it still looks greatw/no peeling. I Por15’d the Frame and then top coated it also. It’s very time consuming and a labor of love but it’s all worth it the end. I also painted the rear inner shell with por15 which makes it easier to wipe down when dirty.