Technic axle corrosion? What happened here? I got my LEGO from storage from when I was a kid (1980s) and while almost all bricks are in good condition, the Technic axles are in a pretty bad shape. They seem to have corroded(?). Please see the attached picture. This has happened to almost all the axles but with different degrees of severity. None of the other bricks, technic or not, black or not, has suffered this.



Any idea what might have happened and how to prevent this?

EDIT: They were stored in plastic bags sorted by color (one bag per color) inside a larger canvas bag in a non-lit, dry environment (garage). All other bricks seem to be fine, regardless their color. Stickers that had been applied survived very well (bright colors) and still hold strongly. Once I got the collection back I mixed the bricks and ran them under warm tap water and let them dry on a towel on the floor for a day. These were the only bricks that were affected.
It appears from the photo that there may be some "blooming" where the axles have changed color? You say you rinsed them, but I wonder if you noticed whether the axles felt oily or sticky at all beforehand?

This would be consistent with the kind of deterioration that is common with Polyvinyl Chloride (PVC), a kind of plastic that was once common in toy manufacturing. I don't know for certain that these early axles were made from PVC, but I do know that LEGO did formerly use PVC for some non-brick pieces, and I have seen similar deterioration on other PVC items. This is a known problem with Barbie dolls, for example.

PVC typically has a plasticiser added to it to make it flexible, usually dibutyl phthalate. This plasticiser gradually "leaks" out of the plastic, leaving it discolored and vulnerable to deterioration and creating gasses (like hydrogen chloride) that will attack other PVC and hasten the process. Heat and light will accelerate the breakdown, and you indicate that these were stored together in a plastic bag. That might have contributed, as the gasses and plasticiser were trapped in contact with the pieces.

Phthalates are toxic and are now regulated in the US, EU, and many other countries. LEGO no longer uses PVC except in some limited applications like the insulation for electrical wiring. LEGO was one of the first companies to begin phasing out the use of PVC, in the 1990s.

To slow the deterioration of PVC, keeping it away from heat and light will help, as will keeping it ventilated to remove the harmful gasses produced by the plasticiser.