Good to hear that Felix lube works so well. I wanted to make some once but couldn't find any sodium stearate. I have found it online now though. Anyway, that's how I ended up with stearic acid.

Interesting observation (reading back a bit). Lanolin is used in this recipe. Could the lanolin be responsible for the corrosion? Once desalted, lanolin can be used as a rust and corrosion inhibitor. Lanolin is itself acidic as in being composed of a high proportion of saturated fatty acids. Stearic acid is a saturated fatty acid which I thought was a constituent of lanolin but I don't find any reference to it so I must be mistaken.

Anyway, I think I shall get some sodium stearate but your results using stearic acid make me think I should go that route. Stearic makes for a pretty good lubricant.