Cleaning corrosion from polished cast iron parts

[Nick WelburnParticipant @nickwelburn]

I’ve got a few finished castings that have been mirror finished and now show traces of corrosion. The light stuff is coming off with autosol and a jay cloth.

What’s best for the heavier stuff? Steel wool?

[Nick WelburnParticipant @nickwelburn]

[bernard towersParticipant @bernardtowers37738]

Try garraflex blocks in different grades.

[john halfpennyParticipant @johnhalfpenny52803]

Scotchbrite pads from your local automotive paint supplier

[Ady1Participant @ady1]

You'll need to protect the exposed metal "instantly" with a film of oil or something, cast iron is very prone to flash rust

[David-Clark 1Participant @david-clark1]

Years ago I used a cleaning solution from ArcEuroTrade. Wipe it on, leave it a bit and wash of with water.

[Neil LickfoldParticipant @neillickfold44316]

The corrosion often creates areas that have oxidised and that is effectively metal removed. Unless you take all the surface area down to the minimum of the depth of the corrosion, it will still be there. Garraflex or the rubberised abrasives are good or non flat shapes. On a flat surface, you will need another flat surface to repair it with. If you just want to shine the surface only and are not concerned with it's flatness, using Autosol , but thinned with turps or a very light oil, like plain unscented baby oil, and using soft material like a lens cloth, will restore the finish. But it takes time. Paper towels and even synthetic clothes material will creates scratch marks. Water will make cast iron rust in humid conditions within a few minutes. The other option is to use an oil based diamond polishing compound and soft balsa wood. Using the makers of the diamond thinning agent or baby oil works great too. The balsa will absorb the diamond and then behave like a lap. Lapidary diamond is water based, so I avoid them for cast iron work and other surfaces that corrode very easily. Balsa wood and Autosol also works very well, and you can see and control the area you are polishing. I get a small pack of mixed sizes of balsa wood from the hobby shop and it's about 4 inches to 6 inches long with varying shapes etc. Usually something in there is about right for the job. Keep each piece with the abbrasive type. I don't mix the abbrasive grades.

[old martParticipant @oldmart]

Posted by Ady1 on 11/03/2022 17:21:06:

You'll need to protect the exposed metal "instantly" with a film of oil or something, cast iron is very prone to flash rust

That is true, I used to clean up and deglaze cast iron brake drums in the kitchen sink with fairy liquid and wet and dry. There was an instant covering of light rust in the drums even when rinsed under the hot tap, and the insides of the stainless steel sink would have to be scoured with a brillo pad to remove the CI rusty dust. The rust inside the drums mostly came off simply by rubbing with a rag or tissue paper.

 I would use the Solvol Autosol as recommended already on a polished CI surface, there is no water involved.

Steel wool will help, but is unlikely to result in a polished surface.

 

Edited By old mart on 11/03/2022 18:20:27

Edited By old mart on 11/03/2022 18:21:53

[Nick HughesParticipant @nickhughes97026]

This stuff is good :- Belgom Chromes

I've used this and the Belgom Alu for years on my motorcycles.

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