The balance rail posts protrude through the keys and are exposed to the elements. They are not immune to rust and oxidation, and polishing them is not always an option. If rust has formed on your key post it has eaten through the plating and the damage is already done. Luckily, replacing the post is very easy.
We have sourced these posts because they are a drop in replacement for Wurlitzer electronic pianos.
To remove your old post, remove the use a narrow screw and tap out the old post from the underside of the keyframe (it easier to have the keyframe would need to be removed for this). Once the old post is out, insert the new post into the keyframe and tap it in gently with a small wood block (to protect the post) and a hammer.