[Ivy66GT]

A 64.5 owner might sandblast a rusty hood hinge, paint it black and all would look original. For those of us wanting natural colored hinges that won't work. However, you might consider citric acid; see photos.

Picture 1 is one of my hinges as it came off the car. Picture 2 is after boiling it in a 10% citric acid solution for maybe an hour. Straight from the acid it has a nearly black finish but a wire wheel solves that problem and with a coat of clear its ready for use again.

Citric acid in powdered form sell for about $15-20 for 5 pounds. Google it. We have a local hydroponic plant store that sells it. You can buy it as food grade so its not like its dangerous stuff nor is it aggressive; it only takes off rust (and some dirt) not sound metal.

[Ivy66GT]

I forgot to mention, this also works great for nuts and bolts as long as they are not too far gone. That way the head markings will be REALLY correct, not someone's made up version of a head marking.

I had never tried it for such a large and complex part until recently. Borrow your wife's biggest stock pot and take over the kitchen for the afternoon.

[Player]

Gary, you are something else! That really looks amazing!!! Thanks for posting.

btw, is a "hydroponic plant store" just a nursery? Or is it something special?

I think I'm going to look at those pics again...very impressive!

[andrewmp6]

Hydroponic is a type of growing means no dirt everything grows in water.

[Player]

Ah, good to know. I'd definitely like to try this method of cleaning lightly rusted parts.

[Shnate]

Wow looks great!!!!!!I like the black finish. So will it stay? I guess if it comes off with a wire wheel it's probably not very permanent. Why not just sandblast it and then coat it with clear. Will it take grease off of aluminum? I'm looking to polish up my bellhousing while the trans is out. I got it very clean but there are still spots of grease in the crevices.

[Ivy66GT]

Yes, hydroponic is growing plants without water. I think some of their customers grown funny weed-like stuff they sell on the side. Whatever, they use citric acid to adjust the pH of the water used for growing stuff.

The black is some kind of coating similar to a conversion coating formed with phosphoric acid metal treatments. How permanent it might be from the citric acid I don't know since its not the finish I was looking for. It also isn't always formed if the metal is fairly clean to begin with. Wet wire wheeling the parts takes it back to shiny metal.

Sandblasting changes the texture of the surface and the part will forever look sandblasted. The same problem happens if your wire wheel is too aggressive as well but I use a fairly soft, well used wire wheel. Also, I can't get my sandblaster inside the springs and other small nooks to make it look new from any and all directions. Boiling acid gets it clean in every possible spot.

Actually you don't quite boil the acid or it splatters. I keep it at a vigorous bubbling stage just below a rolling boil. That allows you to use a pair of metal tongs to fish around in the pot to see when your parts are 'done' then pull them out one at a time.

[Ivy66GT]

A hiccup in the system did a double post on me. So, I'll erase all the above words and add that the store sells grow lights in the multi-kW range. There are some SERIOUS plant growers out there.

BTW, most citric acid is sold as food so don't restrict yourself to a plant store. It is also NOT sour salt no matter what you may read on the internet. That is in the kosher deli department but its NOT citric acid, its either a sodium or a calcium salt of citric acid so its not even always the same chemical. Neither is it ascorbic acid as some may claim.

For chemical ID you can use the CAS numbers:
You don't want Calcium citrate CAS 813-94-5, or Trisodium citrate CAS 68-04-02; these are sour salt.
You also don't want Ascorbic acid CAS 50-81-7.
These will sort of work but are not as good as REAL citric acid.

What you do want is either:
Citric acid anhydrous CAS 77-92-9 or
Citric acid monhydrate CAS 5949-29-1, (EG-Nr: 201-069-1) which converts to anhydrous when heated above 74C which is what you are going to do when you boil it.

13 ounces of the dry white powder per gallon of water is about a 10% solution which should easily dissolve even before you heat it. When it cools down it will all be monohydrate so either one works the same. Strain the junk out of the solution and re-use it again for your next batch of bolts since its usually good for several sessions. When you are through with it dispose of it as if it were orange juice (although its a bit tart to drink ).

[Player]

lol...that's awesome!