cast iron toilet cistern restoration.

[robgil]

i have picked up a lovely cast iron high level toilet cistern from the bay. its a syphon bell type 2 gallon shanks jobby with a galvanised flush pipe.
it works beautifully and makes that lovely gurgling noise when it flushes.
the only problem is the inside is full of rust where something has rusted away over the years , the inside of the cistern walls dont look too bad but they have rusted and are crumbling in places..
is there anything i can use to kerb the rusting process? perhaps some kind of rust converter or paint? any ideas guys?

 

[chuckey]

The cheapest way of getting rid of rust is electrolysis. For this you will need a waterproof container large enough to take the article filled with water, a car battery charger and a piece of steel. You connect the article to the negative terminal, the piece of steel to the positive terminal, put in container. Turn on the battery charger and add washing soda or caustic soda until the current is 2-3 Amps. Wait a day or two. All the rust will have fallen off and the surface will be a fine matt black which needs to be painted immediately. See :- http://www.practicalmachinist.com/vb/showthread.php?t=183405&highlight=rust+removal.
Frank

 

[robgil]

very interesting reading there Frank , thank you. will the water be heavy in metals afterwards? such as the water left after plating something?

 

[chuckey]

I think the ferrous oxide(red) is converted to ferric oxide(black). Doing this will cause the loose bits of ferrous oxide to fall of. So the remaining water is contaminated with it, which is no worse then rusty iron water pipes* so its safe enough to put down a drain. I would not put it down a well or into a septic tank, because the deposits are bit like sand, they are not toxic but they won't go away!
* Around here all the big (6") water mains pipes are rusting away internaly!
Frank

 

[robgil]

cheers frank , i know what you mean about iron in trunk pipes , i have taken brown showers on more than one occasion when the water men have been fettling with their trunk pipes out on the road and disturbed the iron.

anyhow , ive cleaned the rust down with a wire brush but i think i will try a rust converter rather than a tank of water and battery charger (i dont have a charger) but i will need to stop it from rusting again. would sealing it with some sort of epoxy resin or something similar be a good idea?

 

[Lime]

You could try using a sacrificial anode.
A sheet of zinc connected (connection out of, not in the water) to the cast iron should stop rust.

http://en.wikipedia.org/wiki/Sacrificial_anode

 

[chuckey]

Like your suggestion Lime!. The traditional paint for steel would have been red lead. I think that the best you can do now is to get some zinc rich metal primer. The irony (sorry ) is that the inside can be totaly protected up to the water line with Lime's sacrificial anode but the outside which can be seen, will have condensation on it, so it will be prone to rust AND will have to look nice. Loads of the Zinc paint + loads of gloss finish and keep your fingers crossed.
Frank

 

[robgil]

nice one guys , anode it is.
for the outside though i have been toying with polishing it. i doubt msrobgil would go for it though.