pickling a crank

Took apart my 408 for a piston repair and we got some damp weather (wettest January for So. Cal on record!) that attacked my crankshaft in the damp garage. Developed some scary looking rust on it so I decided to soak it in Vinegar instead of the more expensive ($27/gallon) rust removers. $8 for 2 gallons of white vinegar and a home made box lined with a trash bag turned into the soak tub. I added some wood chips under the bag to try and reduce the dead space so the crank would be fully covered (didnt work). Next time I will just buy 3 gallons....So there are before pics of the shiny journals with rust, and then the after pics. Good news was that all the rust was removed with no pitting, smooth as a baby's butt. Bad news is the once shiny crank is now a dull gray with some obvious stains from a prior attempt to rid the rust with evaporust and paper towels. There are still a few spots that I didnt catch (inside the holes) but it was getting late and I had to pack it in. After I pulled it out of the bath (3 days) I gave it a scrubbing with a green pad that took all the rust off with easy, more like wiping it off, and then a sponge bath with a baking soda solution to neutralize the weak acid of the vinegar. It did bubble up a little in places showing the neutralization process. Acid dipped parts flash rust very fast so you have to neutralize and then coat in oil or rustoleum primer or other rust proofing. I sprayed mine down with penetrating oil and put it in a draw tight kitchen trash bag, just the right height. hopefully it will survive a few more weeks until I get the time to reassemble. I wont store it naked like that again. The gray staining may have been a result of it being in the drink too long. Ill monitor it closer next time. Next up is a pile of connecting rods.

Polish time.

What brand crank and what did the piston need repaired?

I dont know what polishing would accomplish, its already smooth? Sure would look better.....I think 3 hours may have been long enough.

You should have used washing soda and water and a battery charger I works great for machined surfaces and wont remove any material.

Apple cider vinger is twice the strenght. Next time add water to cover the part.
brians idea works great with the washing soda and 12 volts also.

Remember this thread?

The Power of Apple Cider Vinegar for Rust Removal

Getting crank micro polished may not be a bad idea, just because you can't feel the difference doesn't mean the babbit surface on the bearings won't... WD-40 used with 1000, 1300, followed by 1500 grit sandpaper with and a shoe string wrapped around it and hours of elbow grease will put the new back on it, if you want to go cheap. If it acts like it needs anything coarser than 1,000 grit to bring it back quickly, it may still need the high speed version at the machine shop. I recommend cosmoline spray from Fastenal, although another good product for short term storage of parts is WD-40 chain wax.

Garrett Ellison said:

Getting crank micro polished may not be a bad idea, just because you can't feel the difference doesn't mean the babbit surface on the bearings won't... WD-40 used with 1000, 1300, followed by 1500 grit sandpaper with and a shoe string wrapped around it and hours of elbow grease will put the new back on it, if you want to go cheap. If it acts like it needs anything coarser than 1,000 grit to bring it back quickly, it may still need the high speed version at the machine shop. I recommend cosmoline spray from Fastenal, although another good product for short term storage of parts is WD-40 chain wax.

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Agreed! All comes down to how bad do you want to take it all apart again to do it properly vs doing it right the first time. Still.. pretty cool trick for rusty parts though!!

Here's a good read for you guys.

Crankshaft Polishing: Make Sure The Journals On The Crankshaft Are Properly Polished - Engine Builder Magazine

MOPAROFFICIAL said:

Here's a good read for you guys.

Crankshaft Polishing: Make Sure The Journals On The Crankshaft Are Properly Polished - Engine Builder Magazine

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Excellent read, and thank you. Many years ago, my machinist spoke to me briefly on the topic of grinding and polishing on cranks and the proper direction of rotation during each procedure. He told me you can do it at home with the ultra fine technique on a good used crank that mic's in consistently at spec, but that the more time and elbow grease the better. He said that even then, there is still a chance of leaving a burr that can gouge a bearing without being able to feel it. The biggest point he stressed was "The shinier, the better".

If I remember right, you make a cage out of rebar or something similar. Put it in you bin or bucket whatever size you need. Then you put your part in with the positive lead attached and then attach the negative to the part. Fill with your mixture of washing soda and water. Make sure the part is submerged completely. I used a 2 amp trickle charger and it worked great. I may have some of the particulars wrong as it has been about 10 years since I did it, but this was the basic setup. Look around on the net, you will find the process.

Here's a link.

Jack

I used a big plastic bin 25 gal or so put in 15 gal water then boil 2gal of water and put in a couple cups of washing soda so it mixes up real good than dump it in the tub of water, throw in my part with the neg wire on it and hook the pos wire to a break rotor or large piece of sheet metal and after a while you have to clean the sheet metal because the rust will be pulled off you part and collects on the sheet metal and the process stops working till you clean it off. Cleaning a cage would be a pain.

I had an old machinist tell me to use deisel and acetone. Said he used this to free up old tractor motors that had been sitting out for years.
No corosion after removing it like vinergar.

I'd try a little chrome polish with a soft cloth. no really I have. nice and smooth with a little work and no metal removed.