A-arm rust pitting at Elphant Racing Polybronze races attachment area

[RWebb]

since we have a bunch of polybronze bearing questions active right now, I thought I'd post this one. it might be of general interest and I know Chuck monitors the list.

After pulling off the nasty polygraphite bushings on my A-arms,

I discovered some rust pitting on my A-arms. It is right where the polybronze races get epoxied down onto the arm tubes. Here is one example at the front of one A-arm:



The red lines point to black marks made with a Sharpie marker by tracing along the top tube and bottom flange of the Elph. bearing race, so the interior surface area between the black marks shows the surface where the epoxy will (hopefully) bind the bearing race to the A-arm.

My question is: [1] did I do a good enough job of exposing enough bare metal to get a good JB Weld "seal" (adhesion seurface)?

if not, then what do I do? the pits are sunken in a bit and cannot be reached by sanding (I spent 3 days sanding...).

It seems like there is plenty of bare metal to me -- but I'm not trained in this stuff....

It seems like the black paint inside some of the pits and rust elsewhere should not be a problem... my thought is that the epoxy should fill in the voids pretty well and seal up the pits even if the paint in them does not provide much of a secure surface for adhesion to the race.

[RWebb]

Here is a close up:

[RWebb]

I have another question too.

[2] There is rust that I cannot get to in the recess of the joint between the A-arm tube and the flange. The bearing race has a sharp 90o profile and will not intrude into that space. The JB Weld epoxy should fill the cross-sectional area between the race and the pictured recess. That ought to seal off the rust.

But, I could use a hypodermic needles and and put rust converter in there. Then the rust would be changed to a polymeric compound. I can easily sand off any rust converter that extends to where the race will sit.

Do I need to do that?

Here is a macro photo of that area.

[RWebb]

another pic of that recessed joint area...

[500_19B]

I have not worked on the A-arm yet, so my comment may be of limited value. However, I have always had great success with a brass wire wheel in a drill. (I have also used a small one in a Dremel tool on occaison - they don't last long though).

It SEEMS to me from my previous experience with other parts that the wire wheel would do a good job on that recessed corner groove... However, if you do use the brush, you may still want to follow up with conventional sanding in order to get a shaper-tooth profile for better bite of the epoxy.

[euro911sc]

This is where bead blasting comes in handy! The pits will create more area to bond to so I would not worry about the pits as long as they get cleaned. If not blasting, then the brass wire wheel or cup works well. Sand paper only goes so far and does not go into pits or dimples as you have found.

You can use Naval Jelly to convert the rust and the remains simply wipe off. Make sure you wipe it clean after that I would not worry too much about it.

Best regards,

Michael

[RWebb]

Thx, BUT:

I used both hand and Dremel mounted brass brushes already - for quite a while, before taking the pics. They are not getting into the pits or the joint recess very well -- the pics show that.

I do not own a sand blaster.

[surflvr911sc]

most powder coaters have their own blasting booths, they look like they could use a nice powder coating anyway; you know, "while you're in there."

Other than that, a rust converter (POR15) or cross your fingers. There is a lot of metal there, so once it's in JB Weld it will take longer than you will be around to get through it, but that's not a place that you want things falling apart either.

[glennspiegler]

Recently did this project. Be careful not to remove so much metal sanding that you loose the snug fit you get with bushing to A arm. After JB Weld your pitted areas won't see moisture or O2, so your rusting problem should be slowed dramatically.

[GaryR]

With a clean surface and JB Weld I wouldn't worry about a thing...

[BryanM]

if it worries you,and having it media blasted is too much trouble, there's a great product called evaporust that will get rid of the rust. the first time i used it, i got it from caswell plating. more recently i found it at my local harbor freight. i was skeptical too, but it truly works.

[BryanM]

i found an example of the evaporust in use. this is the oil fill can from a 912.

[RWebb]

Originally Posted by glennspiegler

Recently did this project. Be careful not to remove so much metal sanding that you loose the snug fit you get with bushing to A arm. ...

yup - that's exactly what I'm concerned about.

It would be difficult to powder coat them. I'd have to remove the ball joints (or have it done at a machine shop) and then I'd have to worry about the powder coater getting stuff in the splines, etc...

Sometimes it is a hassle to live in a small town...

Also, I am on a pretty tight budget sine the economy crashed and it would be hardship to pay for both these things on top of everything else...

[Wavey]

Randy, I'd definitely go with one of the chemical rust removers - very cheap, very effective, finds it's way into every nook and cranny. Kleen Strip makes a product called Rust remover - local AutoZone has it in 8-oz. bottles for +/- $6. I'd do a final water rinse the thoroughly blow dry the area right before JB-ing the races on. I definitely wouldn't remove any more metal by sanding or wirebrushing.

[sjf911]

Having just removed PB races from my A-arms, I don't think I would worry too much about it. The JB weld does an admirable job of binding and sealing the races to the A-arms.

[SC-targa]

You guys are over analyzing the "problem". Are you guys seriously concerned about that little surface rusting on something that will be encapsulated with epoxy?

Randy, while I have always respected your opinions on a wide variety of subjects, I think you've put way too much effort into cleaning up this shaft.

While I am surprised that there was such deep pitting, and so much of it, I really believe that there will be no measurable additional corrosion once you get it all sealed up with epoxy.

On the plus side, the pitting will allow the epoxy to have fabulous grip on the A-Arm.

Regards,

Jerry Kroeger

[juanbenae]

you can get this metal etch product that you mix with water (or use "uncut") that will remove the rust. it worked wonders on my car trailer before i repainted it. the one i used was a jasco product in a with plastic bottle with black writting. i would think that would remove the rust w/o the problem in loosing material with sanding or grinding wheel.

[RWebb]

Originally Posted by SC-targa

You guys are over analyzing the "problem". Are you guys seriously concerned about that little surface rusting on something that will be encapsulated with epoxy?

Randy, while I have always respected your opinions on a wide variety of subjects, I think you've put way too much effort into cleaning up this shaft.

* * *

Regards,

Jerry Kroeger

Well, thanks. But I'd rather be safe than sorry. For the record, I don't have an opinion, as I lack data with which to form one.
And... I'm a scientist, so I am "prepped" to analyze things -- a lot...
The "cost" to over-analyze is nil. It took me a few minutes to take the pics and post. It costs no dollars to do so as I already own a digital camera. Third, the amount of delay in completing the project is slight.

Chuck's instructions say "Be sure to remove paint and any surface irregularities on the section that contacts the race. The control arm end should be clean, grease free and smooth to the touch. Use sandpaper and degreaser as needed to ensure good adhesion..."

Now, I do have irregularities, and the paint inside the pits has not been removed.

So... is it good enuff? That's my question.

[175K911]

Have you called Chuck, and email him some pics? I'm sure he'd be more than happy to answer your question directly which would narrow the choice of options quite quickly.

[RWebb]

Yes, I thought he might see this as he browsed Pelican, but I also Emailed him a few minutes ago.

The Evaporust looks interesting. It apparently is not a rust reducer (converter) type product, but instead forms a chelate (like hemoglobin) that removes the rust.

I'm not sure that "the pitting will allow the epoxy to have fabulous grip on the A-Arm." It might. But that will depend on the adhesion to the paint in the pits, and to the rust and/or reduced rust compound in the other pits. Some seem to have paint in them and others, rust.