Rusty mold

[Echo]

Oh me.:-( I won a mold on eBay. Got it cheap. Haven't received it yet, but on close examination of the pictures, it appears to be fairly rusted, and pitted. Oh me. I don't even have it in hand yet, but am sure that it will need some tender ministrations to get rid of the rust. I know that pits are the pits, and I won't be able to do anything about them, and hopefully the cavities aren't pitted, but I'm guessing at least one is.
If that is the only real problem, then I will have a 3-banger instead of a 4-banger, and I can live with that. Otherwise, what suggestions do we have for getting rid of the rust? I have a case of Coke - I guess I could let the mold soak in Coke for a few days, but I'll bet there are better methods of getting rid of the iron oxide. Suggestions, anyone? I'm thinking of scrubbing the mold faces with copper wool, or whatever...

[Hickory]

BarKeepers Friend + tooth brush + elbow grease.

[cbrick]

Here's a lengthy thread but is exactly what your looking for. Worked extremely well for me on a rusty mold I picked up used on the cheap.

Citric Acid Cleaning (http://castboolits.gunloads.com/showthread.php?t=83572&highlight=citric+acid+brass+cleaning)

Rick

[waksupi]

Look up reverse electrolysis. I use it regularly. It has been covered on the board, or comes up easy on a google search.

[imashooter2]

Electrolytic rust removal is the perfect process for cleaning molds. Only the rust gets removed, you cannot further damage the part as with mechanical or some acid methods.

http://www.smex.net.au/Reference/RustRemoval02.htm

A quick and easy set up I have used several times:

http://home.comcast.net/~imashooter2/pictures/ERR-out.jpg

http://home.comcast.net/~imashooter2/pictures/ERR-in.jpg

The trickle charger shown works over 24 - 48 hours on heavily rusted items, faster on light rust. A 10 amp charger does heavily rusted stuff overnight. The higher the amperage on the charger the faster it works, but the wires will need to be larger and the solution boils off so needs to be watched. Use a big enough container.

Washing soda in water is the preferred solution, but baking soda works in a pinch. A couple tablespoons to the gallon is good.

[cbrick]

So your saying that citric acid will damage the mold?

Rick

[Le Loup Solitaire]

Coke like in Cocoa Cola has Carbonic acid in it. It is a weak acid. Citric acid is found in fruits. Another one that is around is Acetic acid which is found in vinegar. The basic rule is that acid regardless of the type will eat away rust and metal. So if used in a mold that is exactly what will happen. Stick with the advice about using electrolytic rust removal as it definitely is the best way to solve the problem. LLS

[captaint]

Based on advice I got here, I tried good old Naval Jelly on a surface rusted mold. Worked great. Let it sit per directions (maybe 5 mins) scrubed with toothbrush & soap - good to go. Casts great wadcutters.. enjoy Mike

[imashooter2]

So your saying that citric acid will damage the mold?

Rick

I did not say will, I said can. Citric acid etches iron and steel. Used with care and in weak solutions, the etching is minimal, but it still occurs.

[cbrick]

I have now cleaned 3 molds in the Hornady Sonic Cleaner, not with their expensive citric acid solution but with a mixture of citric acid and hot water, 5 minutes in the machine/solution, rinsed and cleaned with a nylon brush and denatured aclohol.

1 used RCBS rusty mold was cleaned this way and it worked so well I cleaned my next 2 new Lyman molds of oil this way. Worked perfectly, 10 minutes from opening the boxes and I was pre-heating them to cast. Zero damage or etching, zero oil (or rust). left on them.

Rick

[John D]

Where can one purchase Washing Soda? I have a mould with some surface rust. I'd like to try this method. TIA

[waksupi]

You can get washing soda in the laundry detergent section of any store.

Citric acid will indeed etch steel. I recently soaked some old dull files in citric acid for a day, and they are once again usable.

[cbrick]

Citric acid will indeed etch steel. I recently soaked some old dull files in citric acid for a day, and they are once again usable.

And I soaked three molds in citric acid for 5 minutes, and they are now quite usable.

Rick

[imashooter2]

And I soaked three molds in citric acid for 5 minutes, and they are now quite usable.

Rick

A weak solution used with care.

You claim zero etching, but that cannot be true since citric acid etches iron and steel. What you had was etching that did not hurt the performance of the mold.

[10 ga]

White vinegar, 1/2 cup to gallon, soak overnite well covered with solution, scrub with toothbrush. Another way is heat and cast a few, then use a toothbrush and while mold hot scrub with OJ, comes clean quick. 10

[Echo]

Thanks to all for your suggestions. I will update the thread when I've massaged the (358477) mold, but I have to receive it first!

[hiram]

http://www.evaporust.com/

[Charlie Sometimes]

Sometimes those E-Bay pictures make grease coated molds appear badly rusted and pitted. Improper lighting doesn't help them either. Wait until you get it to see. You might be jumping the gun.

[mooman76]

I've got a few deals on ebay on rust moulds. I've been lucky though. Sometimes the pictures look worse than the actuall product and I've only had to deal with minor surface rust in the cavities. A pensil will take care of minor surface rust.

[JFrench]

I have used both processes to remove rust. The electrolytic process converts
red oxide to black oxide. After removal from the solution the parts will have a black sootie coating that can be washed and lightly brushed away. Any brushing should be done with great care. I use lye to allow the current to flow in the place of washing soda. With lye great caution should be used.

If you use an acid dip the progess should be monitored often. I over etched a pair of wrought iron nail nippers once and you could see the wood grain appearance to the metal.

James

[HangFireW8]

I can't believe anyone didn't mention Salt + Vinegar.

Just keep all metal fully submerged, and rinse very thoroughly with hot water when done, apply rust proofing immediately. Check mold face flatness with a little lapping, chase vent lines with a dental pick, cast a boolit with a machine screw in it and lap a little with a drill driver.

I got several 1-bangers from fleaBay just to get the handles (cheaper than buying handles alone), I restored them this way just for the fun of it.

-HF

[trevj]

Sometimes those E-Bay pictures make grease coated molds appear badly rusted and pitted. Improper lighting doesn't help them either. Wait until you get it to see. You might be jumping the gun.

This!!! ^^^^^^ In spades!!

Worry about dealing with the stuff IF it is there. Pictures are terrible for determining actual condition of anything, unless taken by a true Pro photographer. Even then...

I'd suggest starting with a brass toothbrush style brush and maybe a little oil of one sort or another, if the mold is dirty, and see where it goes from there if required.

Cheers
Trev

[Freischütz]

I used the electrolysis method and it worked well. I did the job in a plastic 1 pint potato salad container.

http://www.frfrogspad.com/homemade.htm#Removal