Asking for Advice about Rear Lower Corner Rust Repair

M

masangui

New Member
Hi, my name is Mariano. I live in Argentina and I like to work on cars as a hobby.
Now, I am doing a panel repair in a rear lower corner.
I have been researching on the net and this forum has been very useful to me. I have read a lot of post here, but I thought that it would be a good idea to write myself a post to know your opinion on the following. I wish you could kindly advice me.
The rear lower corner and the inner wheel arch panel were rusted at the wheel arch corner as you can see in the following photos.

Photo 1A.jpg


Photo 1B.jpg


I have already cut those sections and made repair panels for them. Please, see inner repair panel in position for welding.

Photo 2.jpg


The question is because there is still some rust in the spot-welded lap joint zone between inner and outer panels. I cleaned the rust as well as I could with wire brushes, sand paper, scotch brite, etc but some rust remains as it is quite an inaccessible area.
I was thinking about soaking the complete section in phosphoric acid, then rinsing it with water and drying it. In some webpages I read that after soaking a spot-welded lap joint in phosphoric acid it would be impossible to remove the phosphoric acid completely and that the remaining phosphoric acid would continue to eat the good metal afterwards. What do you think? Please, see the following photos taken from the wheel arch side and from inside the trunk.

Photo 3.jpg


Photo 4.jpg


I am thinking about two ways to proceed:

1) Sanding the surface with 80 grit sand paper, cleaning and degreasing the surface, and applying epoxy primer as it is now. There is tight rust only and mainly surface rust, but there are also pits.
2) Soaking the hole zone (rear lower corner) in phosphoric acid, rinsing with water, drying it very well and applying epoxy primer.

What do you think? Your opinion will be highly appreciated.
 
Hi texasking. Thanks for your answer. I know there is rust inside that seam but I don't feel like removing the spot welds to open it at this moment. I was looking for another option, although it would not be the best one. What do you think about soaking the entire section in phosphoric acid and scrubbing it as needed to remove as much rust as possible? I think I can manage to make some kind of a container to dip the hole section in phosphoric acid and after doing that I can dip, in the same way, the entire section in water to remove the phosphoric acid and clean it very well. Then, I would dry it with rags and hot air and blow the entire seam. Does this sound as an acceptable plan? The phosphoric acid I have is a metal prep that seems to be quite diluted.
 
masangui said:
Hi texasking. Thanks for your answer. I know there is rust inside that seam but I don't feel like removing the spot welds to open it at this moment. I was looking for another option, although it would not be the best one. What do you think about soaking the entire section in phosphoric acid and scrubbing it as needed to remove as much rust as possible? I think I can manage to make some kind of a container to dip the hole section in phosphoric acid and after doing that I can dip, in the same way, the entire section in water to remove the phosphoric acid and clean it very well. Then, I would dry it with rags and hot air and blow the entire seam. Does this sound as an acceptable plan? The phosphoric acid I have is a metal prep that seems to be quite diluted.
Click to expand...
I hope this doesn't sound harsh, it is not meant to at all. Sounds like from your initial post that you know the answer, but we're hoping for an easier answer. There isn't one.
It is a dilemma every restorer faces.
The question is "is spending the time and effort to fix this correctly worth it?"
If not dealt with properly, the rust will continue. Will that affect the appearance or structural integrity of the panel? Will you be ok with the decision a few years from now?
Only you can answer that.
 
Dean Jenkins said:
I hope this doesn't sound harsh, it is not meant to at all. Sounds like from your initial post that you know the answer, but we're hoping for an easier answer. There isn't one.
It is a dilemma every restorer faces.
The question is "is spending the time and effort to fix this correctly worth it?"
If not dealt with properly, the rust will continue. Will that affect the appearance or structural integrity of the panel? Will you be ok with the decision a few years from now?
Only you can answer that.
Click to expand...
20 years ago I did my first restoration, a 1955 Chevy Belair. It came out beautifully! Frame off, new everything, custom interior. I spent $30K on the project back then, which must be double that by now.
I was painstaking in almost everything. Every nut, bolt, washer and screw on the car was replaced. The under hood paint was a slick as the exterior.
I took it to local car shows (won best in show one time!) and cruise in's. It was awesome!

See pics below.

During the body work, the body/paint guy and I saw rust in the inside of the doors near the bottom. It wasn't that bad, hadn't gone through the door skin. We agreed it would take a lot of work to pull the skins off and fix it correctly.
I decided to just have him spray some rust stopping compound on it (whatever that was in 1999) and call it good.

2 years after the restoration, rust bubbled through the exterior paint. It was awful! I was remorseful and embarrassed. This was avoidable.

I vowed "never again."

Everyone is different, with different goals for their car project. But, I thought I would share my own experience with taking a short cut. Never again!

55 Full Side cropped.jpg


55 Doors open cropped.jpg


55 engine compartment cropped.jpg
 
Hi Dean. Thank you very much for answering to my post and taking the time to write about your experience. I appreciate that!
I must say that that car looks great!
About your comment that it seems that I know the answer but I am asking anyway, it is not harsh to me at all. I must clarify, at this point, that I have no experience in car metal work and that this is my first rust repair. So, that is the reason why I am asking.
The patch you see on one of the photos is the first one I have ever made in my life. It turned out great though. I understand its appearance might be misleading about my experience doing car metal work.
In order to do this rust repair I have been researching on the Internet but it seems that there are a lot of different opinions about how to deal with rust, specially in lap joints and if phosphoric acid would remain into those joints after treating them causing problems in the future or not. That's specifically why I am asking for opinions about this particular repair.
Anyway, I understand that what you and texasking suggested is a fail-proof way. So, I will take your advice into consideration. Thanks again.
 
None of those products are likely to clean that up in the joint, and epoxy won't stick to that kind of rust. Rust in the deepest pits is what you most need to get rid of, but rust in the bottom of the deepest pits is the last part that those products would get to----if the product could get to the rust in that seam.
That will get wet everytime it rains, or even when you wash the car. Hard to say how long before rust pops through, because we don't know how deep those rust pits are.
 
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