Why do my pinballs keep rusting

Ok I just finished my complete restoration on my Harlem globetrotters back in may and have put in 2 different balls.1 from pinball life and now ninja and both have became rusty in no time at all.none of my other games have this problem at all. How do I remedy this problem. Do I clean or replace the ball trough on harlem or are just pinballs cheaply manufactured nowadays. Please all suggestions are greatly appreciated.

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As you can see my trough is beautiful and dont see anything that would cause this rusting

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I just cleaned this new one with rubbing alcohol to be sure so let's see how this goes

I'm running 2 smaller dehumidifiers and it stay around 58-60 % the in the summer but never have had any problems with my balls ever.

It is in the basement my game room

Will be going to Walmart tomorrow and buying a couple damprid tubs.thanks for the advice. This stuff looks amazing.

I wish but these balls are pitted and rusted soooo bad.look like they are over 30 years old in 2 weeks.

Yes they are Ninja's