Cleaning brass corrosion from caseback threads

[ManSkirtBrew]

Suggestions on this? Baking soda, water, toothbrush?

[Klassiker]

Pure water and a toothbrush would a gentle way to start and remove the worst of it. I don't know of anything which will get the threads perfectly clean and shiny, but an ammonia-based cleaner, baking soda and lemon juice are all worth a try and will not make things worse.

[Waggy]

I raised this question a while ago, please see link below, this may be useful:

 

 

[Waggy]

Quick update,

Last night I had a heavily corroded rotor with thick dark green scaling on it (looked like shiny bottle green glass), I tried to scratch some off with a finger nail, but it didn't budge so I dunked the whole rotor in regular store white vinegar for around 30 mins. When I looked after the 30 minutes I saw that the green corrosion was now more of a lighter matt jade green colour with white frosting (??) around it. Whilst still in the vinegar I used a bit of pegwood to poke at the corrosion (more out of curiosity than a serious attempt to clean) and to my surprise most of the corrosion crumbled away easily. A further 30 mins in the vinegar and the rotor was completely corrosion free. The exposed brass that had been lying under the corrosion was clean and shiny and the nickel (?) coating on the rest of the rotor was not damaged at all. Great result and my go-to solution from now on, much more sympathetic than using abrasive methods. Thanks to all that suggested this.

[CYCLOPS]

Parson's ammonia for metal cases....