The white powder material has been identified by Yamaha as sodium sulfate some time ago.
I get it on my 2 micron VST filters and the VST float and walls of VST tank, but so far no trace of it in my 2 micron racors. Meaning it occurs downstream of the racors and not from gas supply.
If aluminum was involved, what are gas tanks made of ?
I clean the VSTs and reuse them. It's a two part device that snaps together via O ring seal. This is a easy DIYer job, even on the boat on the water. Original VST filters did not snap apart, apparently changed due to offering a cleaning solution. The fileters are not cheap (i.e. relative to monster racors)so it makes sense.
Yamaha recommends to keep VST tank empty off season. I leave it empty after changing VST filter season end. Before restarting in spring, hand bulb pump it full until float shuts off fuel.
I think high heat is involved since the VST sits under cowl and motor sitting in sun all the time with no air flow, boat gas tank compartment not the same - very cool. Little time relatively speaking with motor running so doubt it from motor generated heat and also cowl is ventilated when motor is on and boat is moving. Others suggested it is high heat and vacuum, still others say powder is from perhaps stray current as tank is reported as being ungrounded.
Insides of my tanls are pristine, no corrosion at all 5 seasons gone. The white powder leaves a trace that once wiped cleaned appears as a bit more shine on surface.
Stabil and the other preservers are for intended purpose.
The VST is easy to drain so can do so before using motor, but be sure to use hand bulb to refill VST, don't let electric fuel pump run in empty tank. And visually inspect fuel being drained.