Here’s one issue that I hadn’t considered until it came up on a Zenith discussion group: Do I need to paint steel parts that no one will see, like push-pull tubes for flight controls? Surely bare steel will rust, but do I need to go to town on paint or powder coat, or will a simpler solution work?

I’m kind of science-y, so set up an experiment today. I cleaned up three pieces of hot-rolled welder’s stock, painted one with Rust-Oleum enamel, coated one with WD-40 Specialist Corrosion Inhibitor, and left the control piece untreated. They’re hanging on the fence, and we’ll to see over time how the different treatments hold up.

My money’s on WD-40. But no wagering, please.

(Update, March 24, 2022) So, six months down the road we have meaningful results:
1. The untreated piece has plenty of surface rust.
2. The enamel-painted looks nice.
3. The corrosion inhibitor-coated piece shows no signs of rust.

So far, I’m not seeing the need to paint steel parts no one will so, so long as they’re coated with corrosion inhibitor at each annual. But time will tell, the experiment continues!