Yeah, 8 months was probably excessive. We’ve had good results on the training and elevation gearboxes on old Naval guns using citric acid in water. The housings are bronze but everything inside them is steel. The ship was decommissioned in 1948 and last year was probably the first time they have been opened up since then.
It only takes about 2 tablespoons of citric acid (it’s a powder) per gallon of water. It’s best to start with water that’s 160-200 degrees F if you’re putting large masses of cold metal in the solution. It doesn’t take long. Overnight is enough. It will probably come out not looking any better than when it went in but the rust and corrosion will be very easy to brush off after the soak. Citric acid is available in the canning sec of grocery stores and through the online resellers. I buy a pound at a time because it’s cheap in quantity. If kept dry it lasts a long time. It’s also not toxic, at least until it’s used, and won’t hurt skin when diluted.
A citric acid solution is also great for removing tarnish from brass. I have used it on brass items including surplus rifle cartridges. At 140-160 degrees F it makes them bright in seconds. After drying and polishing they look new.
