jstecz
jstecz New Reader
2/10/15 3:47 p.m.

I am building an Exocet (Miata based kit car) and I'm in the process of painting/cleaning up the rear subframe, suspension, etc.

My question is... is there an easy to way to clean up the rear diff housing (aluminum)? I'm not worried about it looking like a show car, but the housing is pretty corroded (just rough and pretty ugly looking). It has a lot of fins, etc, so it's going to be hard to get it looking decent regardless, but any good hints? flappy sanding wheels? wire wheels seem to aggressive for aluminum, maybe just sanding with various grits of paper to get a decent finish on it?

My plan is to get it looking decent (not a mirror) and then clearcoating it.

thanks John S.

BoxheadTim
BoxheadTim GRM+ Memberand UltimaDork
2/10/15 4:08 p.m.

I would recommend media blasting with media suitable for aluminum (IOW, not massive abrasive media). That should give you the cleanest surface for a reasonable outlay.

Kenny_McCormic
Kenny_McCormic PowerDork
2/10/15 4:14 p.m.

Wire brushes on a drill will get it down to clean metal and not chew it up if you're reasonably careful. Or you could try a fairly aggressive (acid based) wheel cleaner and rinse it very well before painting.

Woody
Woody GRM+ Memberand MegaDork
2/10/15 9:12 p.m.

Brett_Murphy
Brett_Murphy GRM+ Memberand UberDork
2/13/15 10:50 a.m.

Use dish soap and a bunch of elbow grease.

One of the funny things about aluminum is that as it oxidizes, it forms a very thin and very strong outer layer. I'm not a metallurgist, but I've heard on boats and some other things that this is a good thing and you don't want to remove it.

rjracin240
rjracin240 New Reader
2/14/15 6:14 a.m.

Castrol super clean works wonders on old Datsun valve covers getting rid of caked on oil on inside of cover. Looks like valve was just cast when done. For cleaning on outside use a stainless steel wire brush or if media blasted ensure media has not been used on steel. You do not want to embed into your aluninum carbon steel particles that will cause corrosion later

rjracin240
rjracin240 New Reader
2/14/15 6:18 a.m.

Castrol super clean works wonders on old Datsun valve covers getting rid of caked on oil on inside of cover. Looks like valve cover was just cast when done. For cleaning on outside use a stainless steel wire brush or if media blasted ensure media has not been used on steel parts before using on aluninum. You do not want to embed into your aluninum carbon steel particles that will cause corrosion later. True statement that aluminum will build a film over itself which is called passification this will protect the aluminum but since you said you will be clear coating it it is fine to take that coating off at this point and then coat It

erohslc
erohslc Dork
2/14/15 8:57 a.m.
Brett_Murphy wrote: Use dish soap and a bunch of elbow grease. One of the funny things about aluminum is that as it oxidizes, it forms a very thin and very strong outer layer. I'm not a metallurgist, but I've heard on boats and some other things that this is a good thing and you don't want to remove it.

Yeah, aluminum oxide, but not to worry, it reforms almost immediately on bare aluminum.

Jumper K. Balls
Jumper K. Balls UltraDork
3/2/15 2:37 p.m.

I decided to do an experiment today with alkaline degreasers on aluminum. This comes up here all the time and there are folks on both sides of the fence regarding super clean/simple green ect and the fact that it will or won't discolor aluminum.

One freshly bead blasted cast Fiat thermostat housing submerged partially in a dilute 1/4 cup purple power to 10 cups hot water. I let it sit for ~3 minutes.

 photo 20150302_112808_zpszrijy2bx.jpg

the dark part is what was in the solution.

For another test I took a fresh bit of scrap aluminum sheet. I peeled the protective plastic off and set it in part way.

 photo 20150302_112834_zpsfdx6cjg9.jpg

I will try and find a more acidic degreaser and repeat this test later.

evildky
evildky Dork
3/4/15 2:02 p.m.

WD40 and a scotchbrite pad work wonders.

gohero
gohero New Reader
3/11/15 10:03 p.m.

2000-3000 grit and eagle 1 nevr dull plus a lot of elbow grease.

Keith Tanner
Keith Tanner GRM+ Memberand MegaDork
3/11/15 10:07 p.m.

The diff housing in question has a bunch of cooling fins, scrubbing isn't really an option.

For me, I'd hit it with a power washer then spray it with a silver rattlecan. But I'm lazy At FM, we'd throw it in the parts washer which is basically an industrial dishwasher.

gohero
gohero New Reader
3/15/15 7:57 p.m.
Keith Tanner wrote: The diff housing in question has a bunch of cooling fins, scrubbing isn't really an option. For me, I'd hit it with a power washer then spray it with a silver rattlecan. But I'm lazy At FM, we'd throw it in the parts washer which is basically an industrial dishwasher.

A part washer would surely be a great tool to clean and shine it out. But its very expensive to own one.

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