Hardware Joy-con rumble pack corrosion/leakage

[GrimDim]

I have some Joy-cons that are otherwise in impeccable condition, except for this corrosion near the bottom. At first I thought the batteries were leaking, but it actually seems to be emanating from the rumble pack. The surrounding area is covered in a sort of red dust, and there is a distinct smell upon opening the Joy-con. I can't see any sign of water.

This is a picture of the most extreme case I have:

So anyway, I'm just wondering if anyone knows what the hell is going on here, is this common, what is that red dust, is it hazardous, what is causing this, from what element of the rumble pack is this from, etc.

 

[Shadow#1]

I have some Joy-cons that are otherwise in impeccable condition, except for this corrosion near the bottom. At first I thought the batteries were leaking, but it actually seems to be emanating from the rumble pack. The surrounding area is covered in a sort of red dust, and there is a distinct smell upon opening the Joy-con. I can't see any sign of water.

This is a picture of the most extreme case I have:
View attachment 218107

So anyway, I'm just wondering if anyone knows what the hell is going on here, is this common, what is that red dust, is it hazardous, what is causing this, from what element of the rumble pack is this from, etc.

That is rust water got inside and rusted and all water evaporated