Topic: Rear brake panel finish

[drumstyx]

I'm starting to pick at refinishing some pieces while I accumulate funds for more serious work (head and cylinder machining, etc) and I'm curious about the original finish on some things, as well as some potential mistakes I may have made.

I started at this by working on stripping my brake master cylinder and caliper. Ultimately I ended up soaking it in methylene chloride, wiping off what I could, then while the paint was still soft, getting at it with a wire wheel on my bench grinder. It worked so well (it seems) that I decided that'll be the way to get at some other panels.

Stripping off the paint was pretty easy with the wire brush, but there's a roughness/pittedness to the aluminum underneath, and I wonder if it's from the fact that it's cast aluminum, or if the wire wheel could have caused this. It's not really parallel scratches (though there are some of those, that's fine) so I don't know how it could be from the wheel. Note that I had already started sanding in some areas.

So I started to think that maybe the original finish wasn't polished, but rather painted. Would a good aluminum paint smooth out those bumps and valleys? The finish was pretty beat up towards the ribbed area up top already, so that's why it looks worse than the lower flat area.

Bottom line: What was the original finish of the rear brake panel, and did I damage it with the wire wheel?

[flybox1]

it was clear coated.
send all your parts to noblehops for a vapor blasting spa day 

[Stev-o]

The original finish on the brake panel was clear coat.  You did scratch it up with the wire wheel but it could be sanded to take the lines out and then polished

[drumstyx]

The scratches I'm not worried about, that was expected as I was planning to polish it a bit then clearcoat it. What I'm worried about is the rough-cast texture. It looks like it's either just come out of a really rough mold, or had corrosion pitting.

The caliper and master cylinder have that texture too, to a lesser extent, and I'm wondering if it's because the factory just painted over rough casting, or if the wire wheel somehow makes pits

[jonda500]

the pitting is from the wire wheel - I did that to a clutch cover once, it was a LOT of work to polish it after doing that to it and I didn't completely get rid of all the pitting. I will never make that mistake again! I've heard brass wire wheels are safe to use (make sure you get one with solid brass wire NOT brass plated steel wire!
John

[harisuluv]

A wire wheel does not make pits like that.

If you want to remove the pitting you will have to sand it and work on it for a long time. 

They were clear coated from the factory. 

[drumstyx]

Whether it's from the wire wheel or not, it's going to suck so hard getting into all those tight spots with the sandpaper. I'm tempted to just do the worst of it and get it powder coated...

[jonda500]

I still say it IS from the wire wheel - the (cracked)clutch cover below(top picture) has no pitting under the black paint. I just stripped off some black paint from the face with a wire wheel and ...(bottom picture)
John

edit - click on the bottom picture twice and you will see that it is exactly like drumstyx's pitting! - However, I noticed if you are really careful to only just remove the paint with very light pressure it is possible to minimise the pitting

[drumstyx]

Well....lesson learned I suppose.

It's basically rough cast aluminum now, so I have to treat it like I'm dealing with a newly cast part. I'll pick up some flap wheels to get it done. I've found success knocking things down with some 80 (might be 120...dunno) grit sandpaper, but it's taking a lot of manual work.

The worst part is I did the same to my master cylinder, which has even tighter spots to sand down now.

[harisuluv]

Jonda, I don't understand what you were trying to say.  Are the two pictures the same part, same process?  I don't understand.

[jonda500]

Jonda, I don't understand what you were trying to say.  Are the two pictures the same part, same process?  I don't understand.

The two pictures are of the same part, a spare cracked clutch cover that a PO painted black.

First I took a picture showing a section where I had already removed the black paint by scraping most of it off and then polishing the remainder off.

Then I removed the black paint from the face section using a wire wheel and took a picture of it (bottom picture!).

John

[Rookster]

A wire wheel does not make pits like that.

Yes it does.  The wire wheel causes those exact marks.  A brass wire wheel will make the same marks.  I think it has to do with the speed of the wheel.  They aren't so much pits but areas where the bristles have cut into the surface to different depths.   

Scott

[drumstyx]

I still say it IS from the wire wheel - the (cracked)clutch cover below(top picture) has no pitting under the black paint. I just stripped off some black paint from the face with a wire wheel and ...(bottom picture)
John

edit - click on the bottom picture twice and you will see that it is exactly like drumstyx's pitting! - However, I noticed if you are really careful to only just remove the paint with very light pressure it is possible to minimise the pitting

Yeah, I wasn't easy with it. I saw the pits and assumed it was just what the metal underneath looked like; that it was painted and thick enough that it didn't matter. Either way, at least I'll have a nice big polishing tool set by the end of it. And I'll save the wire wheel for steel from now on.

[seanbarney41]

A wire wheel does not make pits like that.

Yes it does.  The wire wheel causes those exact marks.  A brass wire wheel will make the same marks.  I think it has to do with the speed of the wheel.  They aren't so much pits but areas where the bristles have cut into the surface to different depths.   

Scott

+1  Although I have seen many brake panels with some rough casting in between the ribs, a steel wire wheel will definitely  do this to your cast alloy parts.

[drumstyx]

A wire wheel does not make pits like that.

Yes it does.  The wire wheel causes those exact marks.  A brass wire wheel will make the same marks.  I think it has to do with the speed of the wheel.  They aren't so much pits but areas where the bristles have cut into the surface to different depths.   

Scott

+1  Although I have seen many brake panels with some rough casting in between the ribs, a steel wire wheel will definitely  do this to your cast alloy parts.

Thus is definitely the case too -- the casting was much rougher on a larger scale between the ribs. So it'll be better than new after all this work