Repairing Pitted Early Air Cleaner

[Hardway]

I am posting this in the Body and Paint forum since this is really a paint/finish question.  Several months ago I purchased this Series-1 air cleaner off of Ebay.  I paid a fair price for it, $150 shipped.  I was in the middle of buying a new home so when it arrived I opened it and based on a quick inspection I deemed it was good, placed it back in the box, and saved it for another day.  Recently I unboxed it with the plan of getting it blasted and powder coated.  The picture below shows the original rust and pitting before I dropped it off at the PC shop.

In my haste to move forward I dropped it off, not really looking at the pitting.  Hoping for the best I got it back and of course to no one’s surprise the pitting is still there.  The rest of the air cleaner looks great and the “Pumpkin” color I chose is spot on in my opinion.  Since the pitting is where the decal goes and is most visible when installed on the car I do not know what to do.  Before I do anything rash I wanted to get some owner’s opinions of where to go from here.

The primary reason I bought this air cleaner was because it is the only one I have seen in a long time that had a mint snorkel on it.  Too many are banged up from years of use.  Due to how thin the metal is, once it is damaged, it takes a very skilled person to make it look right again.

At this point I “think” my only option is to blast off the powder coat, fill in and body work the pitting to make it smooth, and then have it re-painted to match the rear cover.  I welcome everyone’s ideas and suggestions.

Edited April 1, 2016 by Hardway

[John Coffey]

Don't bother to blast the powder coating off.  Sand it, bondo it, sand it, and send it out for paint.

[CHL240Z]

I agree with John, sand-filler-sand-paint.  Should look wonderful after that.  What is the color code you used, it is spot on IMO.

Clay

[Hardway]

Thanks for the info guys.  I have read up and since the powder coat is new it should serve as a good base.  Agreed, I love the color.  The color name is RAL Pumpkin.  I can call them on Monday to get the code.

[Hardway]

Well I finally got some time to work on this and so far the results have not been good.  I picked up some Bondo 907 Glazing and Spot putty.  You can see it using the link below.  I used some 120 grit sand paper to knock down the powder coat some and used my fingers to get in to the pitted portions of the metal.  I mixed up some of the putty on my mixing board and applied to the areas that needed it.  At first seemed to be adhering well and I let it dry for 20-25 minutes as the instructions indicated.  Once it dried I went back and started sanding with 220 per the instructions and the filler pretty much just lifted off the surface.  It also pulled out of the pitted areas.  I cleaned it all off and tried again, giving it more time to dry and had the same result.  

http://www.amazon.com/Bondo-907-Glazing-Spot-Putty/dp/B0002JM8PY

At this point I am thinking I need to either get some courser sand paper or possible wire wheel all the powder coat down on the top panel area and use some real panel putty.  That way I can sand it all down flat and hopefully the putty would adhere to the metal. What do you guys think?

[Patcon]

Most of the filler I have seen want a course sanding finish 36 grit or 80 grit minimum. Is the filler you are using catalyzed? Also Bondo does not make the best products anymore...I would go with an Evercoat product

[Hardway]

Hi Patcon.  The hardener is labeled catalyst so once mixed in I would say yes, it is catalyzed unless you are meaning something else.  The spot putty is very light (or its supposed to be) so 36 or 80 grit would be too harsh but I know where you are coming from since it seems like the surface needs to be rougher to get the filler something to grip to. 

I read up on the Evercoat products and you are right, they seem to be favored over the Bondo brand of stuff.  There is a auto paint supply shop not too hard from my office.  I plan to pay them a visit this week to see what they have.

[Patcon]

Evercoat sells plastic fillers and fiberglass products. If you go to a professional retailer see if they can advise you between the two. Fiberglass tends to stick better but is harder to sand. Plastic filler is much easier to sand but may not adhere as well. You really need a filler not a spot filler / glazing putty. They are designed for very small flaws and don't stick as well...

[Captain Obvious]

I'm not a coatings guy, but I have a couple questions/comments:

First, I probably misunderstood what you were talking about with mixing on a board and a catalyst above, but that 907 spot putty is a one part non-catalyzed solvent evaporation process only. If you were mixing that 907 with the cream or liquid catalyst (that you use with fiberglass or polyester filler), I have no idea what would happen. I can't imagine it would be anything good though.

Second, I've been told that powder coating is a difficult surface to adhere to. Tough, hard, slick, non-reactive... All the things you don't want in an undercoat.

[rossiz]

most powder coat is made of powdered pigment "globs" encased in hard wax. the part is given an electrostatic charge to cause the powder to stick in place, then the part is baked in an oven to melt the wax into a continuous coating. 

imagine trying to adhere to the side of a candle... 

if the pitting is bothering you that much, than i'm guessing you may need to bite the bullet and strip it, do the sand/fill thing and then re-coat properly. otherwise between the texture, blending sheen differences and potential peeling, you'll be chasing imperfections forever.

[Hardway]

I made the most of the 3-day 4th of July weekend and got the air cleaner project wrapped up.  I plan on doing an more extensive write up on the restoration but wanted to let you guys know I took your advice and the end result exceeded my expectations.  For the filler, I bought a small tub (cat food can size) of lightweight Bondo filler as the local supply store only carries Evercoat in one gallon cans.  As I said before, this is my first real effort at paint and body work and given that fact I think I did pretty good.