Rust on Ultegra SPD-SLs

Apparently the axle is just plain steel, not SS. Possibly they didn't bother with an anti-corrosion treatment on those internal splines. I wouldn't worry about a little rust inside the hex at any rate, but if the moisture is corroding the threads (between the steel axle and the alloy crankarm), that could cause you problems down the road. Suggest you remove the pedals and check for corrosion on both the male and female threads and mating surfaces. I'd reassembly with grease on the threads and between the mating surfaces of the steel/aluminum.

It's hard to dry off all the places on a bike that can trap droplets. I often just use a damp rag to clean the frame tubes when they need it, rather than spraying down the whole bike.

Nor did they bother to specify the spindle material on their web site (for Dura-Ace either)!

bike.shimano.comproduct. code PD 6800. type .pd road.htmlOpen ↗

The threads seem fine; I've put some grease on. Thanks!

I use blue marine grease on the pedal spindles. Sold for use in boat trailer wheel bearings that see a lot of time under water.

After exposure to water, hit them with WD-40 and do as mpre53 says...apply a light film of grease with a Q-Tip. I have also known guys to clean the hex recesses of fasteners and fill the voids with silicone caulk (available in clear, white and black at most hardware stores).