Removing rust and scale

Paulc20

Impressed by that bath you gave the transmission selectors, I turfed my molasses out on the garden in the hope it may induce rain (it didn't!), so have a packet of washing soda, a 5 amp charger and an old 12 volt battery which would probably just hold enough charge to trial.

Plastic tub holds about 30 litres, what or how much soda do I try? Or just keep adding until she starts to percolate?
OR if enough is just right, throw another handful in?
Thanks for the tip, Dave

I used a 30l tub, about 20l of water and put a bit of washing soda in, probably about a cup. Some of the paperwork said it doesn't matter very much how much you put in, but putting extra doesn't make it work any better.
Paul

Well dun PaulC20

Wot we all like to C

Exhibit 'A' in pix

Gr8 info

cya

You only need the battery if you have one of the new type chargers that have to "see" a battery before you get any output. Don't go much over 5 amps with the current either as you might end up with what is called hydrogen embrittlement which will ruin the parts. As an aside to these methods vinegar works well for rust removal just that it stinks and can be hard to find in significant quauntities, you should see the looks you get at the woolies checkout with a trolley full of 2L bottles

I have used molasses in a 240 litre rubbish bin that way you can shut the lid on it and it doesn't stink out your yard and it works well. I half fill the bin with water put 10 kgs of molasses in and wheel the bin around to stir it up a bit , check your parts in an old milk crate and chuck the crate in. Yank them out in a few days then pressure wash or hose them off or if they're still rusty put them back in. Rusted up nuts and bolts will undo with your fingers and is amazing how well they come up but DO NOT PUT PARTS WITH ALLOY IN THERE AS THEY WILL DISSOLVE.. wear gloves because it is hard to get the smell off your hands. Hit them with phospheric acid afterwards which is deoxidine that you can buy cheap from any pool store or bunnings . Use ppe for that and you will have clean rust free parts. It works well for me.

I have been off air for quite some time and missed this post.
Here's my lazy way to clean off rust, scale, grease and even paint. Molasses works as someone suggested but takes quite a long time. I have been using the system below since the 1970’s and it works fine. I wouldn’t put alloys or machined surfaces in it however. I played with quantities of chemical but have found it not to be too critical and what I suggest will work and should get you started.

You will need 2 plastic lined 44 gal (200 litre ) drums or plastic ones or even a fibreglass bath tub will do you just can’t have metal in contact with the liquid. A good battery charger with an amp meter and alligator clips on the leads, a length of ¼ steel rod about 3 feet long and a piece of 4x1 timber long enough to lay across the top of the drum. Also some tie wire, long rubber gloves and eye protection. Most of you should be able to scrounge all this. You will have to buy one 20kg bag of caustic potash and one 20 litre drum concentrated phosphoric acid. (most chemical companies will have these)

Set up the first drum with Caustic: Carefully add a little water to drum and then a little caustic and stir then gradually adding more caustic and water until all the caustic is added and the level of the solution is about 18 inches to 1 foot from the top of the drum. Set up the second drum with phosphoric: Repeat above process adding the phosphoric and water to about the same level

Method: Take the part you want cleaned and wire brush part of it to get a good electrical connection then attach a piece of tie wire and lower into the caustic tank leaving the end of the tie wire hanging up over the side of the drum then attach one lead from the battery charger to this wire.

Drill a few 5/16 holes along the piece of timber to allow the rod to slide through freely. Lay the timber across the top of the drum and pass the rod though one of the holes down into the solution, clip the other charger lead to the rod and this will stop it sliding all the way through. Check and make sure the rod is not touching the work and is hanging free. Turn on the charger and watch the ammeter. Adjust to get maximum current by just sliding the rod either up or down into the solution. I can’t remember whether + or – to the work, it works both ways only one way is faster.

Relax and have a beer your job is being cleaned

I normally leave the bits in overnight and pull them out for a check in the morning, sometimes really badly rusted or corroded I put back in for longer. Give them a good wire brush and a hose off. If you think they are clean and derusted completely then hang them in the drum of phosphoric and have a few beers. Pull them out and hang up to dry. When dry they should have a light grey matt finish. This finish can be painted directly over. If I am not going to work on them straight away I generally give them another dip in the phosphoric to make sure they are well coated. I have left stuff treated like this laying around for a couple of years with no sign of further rust.

Mike,
Thanks very much for your great explanation,
Just one question how much phosphoric acid added to the water, or ratio?

Jim

Had a lot of trouble locating Phosphoric acid 85%
but finally got a 15L drum from a commercial cleaning warehouse
Can anyone give me a quick run down on ratios and cautions please
to start i have rusted door hinges screws bolts and small parts,
when i have sorted these out i have some larger panels parts to do
Cheers
Jim

Jim
I found that the concentration of phosphoric is not critical. From memory I originally used 20 litres of phosphoric in a 44 filled only about 3/4 with water which worked well. I just added more as time went on if I thought it wasn't working and the bits I was doing were not drying the light grey colour.
I cannot remember what concentration mine was whether it was 100% or 85% like yours so a little trial and error might be needed.
Mike
PS Seeing as you are starting with small stuff I would try a small amount neat to start with and dilute from there. Just remember you are looking for a uniform light grey finish on the parts when they dry out.

Many thanks,
i will try it out,
Have you had any failures or are any types of metal not compatible?
I was thinking door hinges, window winder mechs and the like where there may be spring steel or maybe alloys
cheers
Jim