Wed Apr 2 2008

Polishing firewall

Well I tried just using the blue compound to polish away the oxide, but that didn't work at all. That oxidized stainless steel (it seems odd to say that, but that's what it really is) is really tough and the blue doesn't attack it very well. After that I switched to the green compound and even that took a while to remove the oxide.

After using the green to remove the oxide, I decided to try skipping the white and going straight to the blue. That worked pretty well and resulted in a pretty high shine. It looks like I can skip the white altogether. However upon further inspection, I noticed that the surface of the steel had a bit of a mottled appearance. Sure it is shiny, but the surface isn't smooth. Click on the full sized image so you can see what I mean.

Here is the section I had previously polished. Notice that the surface doesn't have that mottled look. In retrospect, it makes sense that the surface would have a somewhat mottled appearance. I used to be in the steel industry and know that sheets of steel like this are formed by rolling thicker steel sheet through some big, heavy rollers that actually crush the thickness down to the correct gauge. These rollers generally have a slight surface texture to help pull the steel strip through. But this causes the surface texture of the rollers to get transferred to the steel itself.

What all this means is that I'm not going to be able to avoid using the black compound and the sisal wheel. I need to use those to grind off this texture and get the surface very smooth. Unfortunately this means that I have to follow up with some extended polishing with the green compound. The black compound leaves significant (fine) scratches in the surface that take a while to get out with the green compound.

I went over the middle section (under the firewall recess) with the black compound and the sisal wheel. If you look closely you can see little bits of stainless steel embedded in the outside surface of the sisal wheel. Man, this black compound is really aggressive.

I went over the bottom three inches or so of this middle section and polished out all the scratches from the black compound. I decided to call it a night since I was getting a stiff neck and back. I should be able to finish this middle section tomorrow.

As a side note, this polishing is the dirtiest job I've done on the project to-date. Polishing compound dust has been blasted everywhere. It has literally been sprayed up the wall. It's all over the floor. I has covered all my storage organizers and whatever tools happened to be on the workbench. My die grinder is covered in black gunk. This is truly an awful, awful job. Even cleaning the surface between cutting passes creates it's own mess. I've already gone through half a bottle of Windex and have a three foot diameter pile of used paper towels on the floor. It really gets everywhere. I'm using my respirator to avoid breathing it, and I've taken to wrapping a plastic bag over my head to avoid getting it in my hair. The stuff is moderately stinky, too. Not like MEK stinky, but sort of an industrial stinkyness.

Well, at least I'm getting to know what I'm doing. It's been a hard learning curve so far, but at least now I'm making steady progress. I hope to have this firewall completely polished by the time I go out to visit my brother in California later this month.