Goodness. I'd be having a good old fashion come-apart on that deal. I've seen them sit outdoors for years and not look like that. Looks like corrosion from a chemical.
I sprayed gumout in it and had to use an allen wrench to get the main jet to move and then it still took a good 15 minutes of tapping with a screw driver handle to get it out. I knew it was bad after I removed the main jet screw on bottom and when I tapped it to get it out all these tiny white pieces started falling out.
Banjomaniac