2117 rivets are anodized
Which are the most common rivet in our airplanes. (2117)
It was my understanding that they smoke from the heat generated by quickly compressing the rivet. The compression heat changes the alloy of the rivet.
An AN470AD rivet alloy is 2117-T4. After squeezing and the resulting heat, the alloy is changes to 2117-T3 (a bit harder from being worked).
After 1991. Enough said.
And Chemical Conversion per MIL-C-5441 has nothing to do with rivets we use in todays RV aircraft.