DIY Rust Repair

Hello:

I recently purchased a Mondial with significant rust below the fuel filler. I just finished my first whack at repairing the rust, and thought I would post the process here.

--Jeremy

 

First, I taped off the rust area.
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Then I used a Dremel tool to cust the rust out.
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After cutting the rust out with the Dremel, I thought that I would use a chemical rust remover to get rid of any small bits I may have missed. Unfortunately, the chemical rust remover didn't work for me. You're supposed to leave it on the metal for 30 minutes or so and then rinse off thoroughly with water. I was so worried about the rust remover dripping on my car that I didn't leave it on as long as directed. I was also worried that I would not be able to rinse all of the rust remover off.

There is another type of chemical rust remover that supposedly turns the rust into primer (and doesn't have to be rinsed off). In hindsight I wish I had purchased that instead, although I have no idea if it would really work.
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Time for the Bondo!

I used a putty knife to mix and apply the Bondo. I've never used Bondo before, but it really wasn't difficult at all. It's basically the same as applying spackle to fix a crack in a wall.

Neatness isn't important here.
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Locktite "Extend".

 

After applying the Bondo and allowing it to harden, I used a sanding pad to remove the excess.
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After sanding the Bondo I applied Glazing Putty. Glazing Putty is simply Bondo that goes on smoother. I don't know if it was really necessary as I didn't notice a huge difference with and without the putty. Glazing Putty mixes just like Bondo and is applied and sanded the same way.
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After applying and sanding the Glazing Putty, I used a small brush to apply the primer. I then sanded the primer with 1500 grit sandpaper.
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I purchased a cheap airbrush (around $50) from a hobby supply store. The paint I used (from PaintScratch.com) was too thick for the airbrush, and I ended up thinning it out with paint thinner. (I just added paint thinner until it looked right, but I think it was about 75% paint, 25% thinner.) I had never used an airbrush before so I practiced a bit on a piece of cardboard. The paint went on great, but I was a little concerned that the color didn't seem to match as well as I had hoped.
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As a final step I used some Zymol polishing compound and a couple of rags to hand polish the area. The more I polished, the more the paint matched.
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I did the same to a 911 once... 3 months later, all of the rust was back. Used almost the same products as you...

Some things I have learned about rust...

YOU HAVE TO REMOVE ALL OF IT... chemical rust converters aren't really good... Keep dremeling until you see pure metal, then use a rust converter (metal ready/ospho, etc).

Then you have to seal it. Go to a NAPA store and get epoxy primer...this is key...

Then paint...

If you intend to prime with the spray can stuff, and paint with the spray can stuff... it won't last. I have tried tons of times, and slowly learned...


Addendum... I see you didn't use an epoxy sealer...not good. The paint is some what porous...and so is bondo...
I would strongly recommend you sand it down again, and seal it if you want it to last...

Otherwise... looks pretty .

 

I'm pretty pleased with the results as a first attempt, although I'm not 100% satisfied. I made the mistake of sanding a lot with loose sandpaper and my hand, which created indentations in the bondo. I plan on resanding the area with a sanding block. I think that I can get the area looking almost perfect with a little more practice.

My observations and lessons learned are:

* It's not as hard as I thought it would be! If I can do it, anyone can.

* Don't sand with loose sandpaper and your hand. There is no way that you can get the surface completely smooth. (Your fingers will create indentations.) This is a mistake I made. I plan on sanding it back down with a sanding block and repainting.

* Don't use a chemical rust remover.

* PaintScratch.com is great. I am very pleased with the color matching.

* Once you start cutting the rust out, you'll see that the rust area is at least twice the size you thought.

* Between each step I removed and reapplied the tape around the area I was working on. This allowed me to more easily judge my results as I went along.

* An airbrush is nice for blending the new paint with the existing paint.

* Sand after each coat of primer and paint with at least 1500 grit sandpaper on a sanding block. (Do not use your hand.)

* Any imperfections in the Bondo will stand out once the paint has been applied and polished.

That's it. I'll post my final results after I sand back down and reapply the paint.

--Jeremy

 

Still 100% better than how it was before, good work.

 

Nice work, just getting the rust away helps 100%. I am Norwegian so maybe this english do not make much sense!-) However I give it a go.

I think you only uses the base colour and did not use clear paint. On metallic there is just no way you are getting a match without the clear paint. This gives a protective film but also the right color and make the match (a match). Also I use a cardboard and carve out the shape (of what I want to paint) in addition to the masking. In that way you can paint horisontal and diagonal the base and the cardboard cuts the spray off without stopping on the surface and make those small metall flakes apperar factory (thats how they painted it at Ferrari) and match better inn. Also mask when you go for the base and the clear cote approximately 2 cm from where the filler is. That way you do not get a hard border old paint new paint. and polish is for the end finish and rubbing off the dusty eareas not to get the paint the right color..unfortunately. Good job though to be the first time... Keep on the good work DIY is inspiring!

 

Good job.

I've always said that DIY paint fixes are about "fooling the eye". There's no possible way to get a spot/area repair to blend perfectly, especially on old paint. If you can get it to the point where most people don't notice, then you're in business. There will always be people who notice (usually dentists, professional body guys and Corvette concours judges), but short of a full repaint (which will get rock chips that need repairing eventually too!) a good area repair is just what the doctor ordered.

 

Thanks for the masking and painting suggestions!

You are correct, I did not use the clear coat paint. The paint kit I bought from PaintScratch.com included the clear coat, but I didn't apply it as I plan on resanding and repainting the area in the near future. (I think I can do a better job getting the area perfectly smooth...) When I repaint I plan on using the airbrush to shoot the clear coat on to match the rest of the paint.

 

You're right about not being able to blend the paint perfectly. I am pleasantly surprised, however, how well the paint matches.

Right now what really stands out, more so than the paint, is that my fingers created small indentations in the Bondo when I sanded. I knew that I should have used a sanding block, but I didn't have one handy. (I bought a couple of foam sanding blocks, but they wore out very quickly.) I'm going to cut a piece of wood to fit the area that I want to sand and make my own sanding block which should give me a more consistent surface for painting.

 

Hijacking the Thread slightly,

Is that the Blue Mondi that has been on eBay and several other sites over the past 6+ months. If so, how does it stack up other than the rust spot you fixed?

Great job BTW ! ! ! ! !

 

Yep, it is! I watched the car for a year, gave the owner a low-ball offer via email, and got it! (Somewhat to my surprise...) I had never even seen the car in person, although other FChatters had. (I owe Wade a big thanks for his accurate report of the car's condition...)

Since taking delivery of the car I've been going over it carefully. The car is actually in much better condition than I expected. The one rust spot below the fuel filler is the only rust on the car. (I've even removed the weatherstripping around the hood, trunk, and engine compartment looking for more rust.) The car has obviously been repainted, and the paint job is about a 8 out of 10. Again, better than I expected. The car has sat without being driven for some time, however. I've spent a lot of time going through and cleaning the electrical connections. When I bought the car very few of the buttons worked. I've gotten everything to work except for the passenger side window and fog lights. I plan on tackling those this weekend.

The car starts right up every time, the gears shift well (even second). It pulls a little to the right when braking. I still have a lot of work to do on it (major service, all hoses replaced, etc.), but so far I'm extremely happy with the car.

--Jeremy

 

Excellent Jeremy,

E X C E L L E N T ! ! ! !

Drive her in Good Health.

 

Having bought an old mondial ten years ago and fixed her up, great work! Enjoy the ride, its sometimes rocky but worth every cent

 

WAY TO GO!!!!!!

I LUV BLUE MONDIES!!!!


DOUG

 

When sanding bondo,and i am a corvette guy you can use a paint stick for a sanding block and when sanding near an edge never go over the edge and round it off
also once you believe your happy with the primer spray a mist coat of color let tack up and wet sand.Once you wet sand with a sanding block over the mist coat any color that remains are low spots!!!!!!!!!!!!!!!!!!!!.Next time mask off the whole area and fog the paint and clear as you move away from the repaired area that way you dont have crisp lines to sand down

Looks Great Keep working!!!!!!!!!!!

Dave

 

Nice work Jeremy, now you're "blemish free"

I'm still enamored by the beauty of that color on a Mondial.
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