If it's got some aluminium or pot metal, you've probably got a leak and it is corroding. It could just be a leak and it's powdered soap. Do you have a dishwasher hooked up? Is the connection leaking? If the water isn't hot enough, it won't disolve the soap if you use a powdered DW soap. Some of those can really play hell with a low-end disposal.
That thing is shot! They have been making them a black/grey for about 8 years now.
So, It's got to be at least 8 years old or more on a design that was stretching it to get past 4 or so .
If you look inside the galv. steel grinding teeth are gone it is just pushing unground food waste down the drain. I have seen these literally fall off the sink from corroding through. The corrosion is probably much worse where it connects to the stainless steel flange at the top and around the dishwasher connection.
The Badger series is basically the cheapest disposer in the line for cheap builders who put it in just to say that you have one. $70-90 at big box for the Badger 1 & 5 with a 2 year guarantee.
I would recommend upgrading to the Insinkerator Evolution line. They have a stainless steel grind chamber, rubber isolation mounting and many other features. They are super quiet and I consider them to be a very good disposer.
I will second the recommendation to get the Evolution instead of the Badger series. I replaced my 14 year old Badger 1 and once I had it out I got a good look at the condition of the grind chamber. It was shot. The sides of the grind chamber were eroded/corroded away making the slots too large and letting large pieces pass to the drain.
When looking at the Evolution line, I recommend that you go the the insinkerator site and look at the mechanical drawings on the spec sheet to ensure that you do not run into any fitment problems. The evolution is larger than the Badger 1.
I would not expect there to be much of a difference in performance. Everything looks to be the same except for external dimensions, the grind chamber capacity, and warranty. The Essential has a longer warranty than the Compact. If I remember correctly mine is the Compact. I think that I went with the Compact because it was the closest in dimensions to the old badger 1.
What does a larger grind chamber get you? The ability to shove more junk down there before you turn it on?
My last one was a Badger, and it did literally fall off. The dishwasher soap was an issue with it, though, and is fairly corrosive by itself. New dishwasher has a temp assist and always can disolve the soap. Cleaner dishes, too.
I bought the Evolution (?Excel model?) to replace a seven year old Pro77 towrads the end of last year. After the plumber installed it he switched it on for a test and had to re-check the power hookup as he didn't think it was working......it was....good stuff...even does celery and corn cobs.
I found this thread and postings by volsboy77 to be funny and good information about disposals. The guy takes them apart as a hobby. I ended up with the Evolution based on this thread.