I've noticed that the anodized black finish on both my Shimano DA7900 crankset and the same type of finish on my Ultimate AL frame has been bleached or tarnished by sweat. I did a lot of climbing on Mallorca in 30-40°C heat this summer aswell as on Gran Canaria in the winter, and noticed it on the crankset and thought immediately that perhaps the sun had been the culprit in combination with sweat, however there's equal amounts of bleaching/wear/tarnishing in droplet shaped areas on the underside of my toptube - an area that hasn't seen much if any sun. I'd always thought anodized finishes were some of the toughest.

And yes, I wash/thoroughly clean my bike regularly. Usually 3-4 times a week, and I haven't used any strong cleaning compounds either, no degreaser and just a couple of drops of dish detergent on a sponge.. and I haven't been running my bike on a turbo/rollers indoors yet.

Now, what the heck does my sweat contain that ruins anodized finishing?

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12 Canyon Aeroad CF 9.0 ETE
12 Canyon Ultimate AL
11 Cervélo P2

salt ?

seriously though...
I actually have the same "issue". some people have more aggressive sweat composition than others.
I learnt it the hard way (stripped paint from an AL frame, than my look 381 lugs - AL - got the color all "bubbled", when i was running shimano DA7700 the levers and crank would get strange discolorations... and cable replacement was a monthly issue in summer).

The thing is - i live in Israel. so hot and humid... IIRC you are in northern Europe, right? so you do not get to "explore" your sweat as much as where it's hot and humid .
your Mallorca experience has been just that - hot and humid.

Anyhow - this taught me to choose full carbon (incl lugs) frames; carbon crank set & levers etc, which is overall a good idea (going to campy, that is).

don't be alarmed... its natural (for some, anyhow).

Oren.

There has to be chuck norris joke out there for this....

I absolutely agree that different people's sweat can be dramatically different. We had a customer who would corrode Nokons on his De Rosa King in 3-6 months whereas I have been riding the same nokon beads for years with no issues (and I sweat a bit). I think it is both a cleaning issue and sweat composition issue. Sounds like the OP cleans his bike with some religion (like you should!), so def. your sweat. Maybe just get a lighter bike than you won't have to work as hard?

UV light can affect the a cheaply conducted (hence thin) anodization layer too, but one would hope that not to be the case with the brands named.

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Bikes: Raceur, Beateur