I bought a new 25 year old Webra Speed 20 Marine engine awhile back. It was stuck worse than epoxy when I got it. I slow cooked it in anti-freeze just to be able to knock it loose enough to disassemble it.

After everything was free from the crankcase casting, I de-burred, filed, sanded, brass brushed, scotchbrighted and then finally soft scrubbed with Cameo sink cleaner, scrub rinsed it in fresh water and the aluminum was looking FRESH!

I thought for safety reasons just to be sure everything was out of the aluminum and the nooks and crannies, the only thing I could think of other than hitting it with brake cleaner or anything else that could be caustic, to save the bright finish, I boiled in a teflon coated saucepan of tap water, thinking that should do it.

After ten minutes of a rolling boil, I reached in with my tongs and fished around and pulled out what I thought was disaster to the finish.

Looking at the surface I notice these tiny little blooms of crystals here and there, and the aluminum started to go dark on me.

I assumed because this was a casting, something was still in the aluminum...albeit anti-freeze or cleaning cleanser.

I soft brushed it again with just dish soap to remove all the blooms, rinsed the pan, and boiled it again with fresh water.

Second time around it developed a rich, burnt iron color that seems hard as nails - but there were no more crystal blooms.

Thinking I am safe now of anything trapped in the aluminum, I liked the color better than the bright finish - and I know nothing else could have survived that the engine will ever see except nitro and exhaust tempuratures.

To be double sure I fired up the oven to 450 degrees with the case on a cookie sheet and let it bake for a half hour just to see what would happen to the surface. The only noticable difference was it picked up a gloss, so whatever it is thats on there melted a little I figure, and got a harder surface.

I haven't done anything to it yet as far as brake cleaner or scrubbing...so I dont know how durable the finish is on this, or if it is anything to be concerned about when I go to heat it up again to install the crank and bearings.

Take a look at the pictures and you decide what happened or what should be done.

What do you suppose caused this? The anti-freeze or the sink cleanser?

The first picture is what it looked like as I recieved it. The second pic is what I have right now. Whatever caused it is now on the surface of the aluminum. And it is evenly coated with color, inside and out, cast surface or machined.