Perplexing ground noise

I have a 1999 Nissan Pathfinder SE and right now I'm running a set of Infiniti components in the front and a set of Kickers in my back doors. They're powered by a 4x90 power acoustik amp. I've also got 2 rockford fosgate 12s running off a Sony Explod 1000w class D amp. My head unit is an Aiwa CDC-MP3. That's probably all superfluous but I figured it's better to give too much info than not enough. Anyways, here's my problem. My system was working great until a few weeks ago, when I went through one of those power washes at a gas station. I had my stereo completely off so that my antenna would retract and not get ripped off. Anyways, when I came out of the car wash, I turned my stereo back on. It made a few LOUD popping noises and then a constant very loud hiss. I turned it off and went to lunch. When I came back out I tried turning the stereo back on. At this point it started working, but now I have some SERIOUS ground noise. I didn't really have time to look at it for a couple weeks, but when I finally did pop my hood to look, the positive terminal was covered in a whitish greenish powder. I know that it wasn't there before the stereo blew up because the system had worked for about 6 months and I had just recently been under the hood. The power cable IS fused and the fuse didn't blow. So, to get to the point, I thought that ground noise was a physical problem? Nothing changed physcially. Could some water have leaked somewhere and slightly shorted my amp? And what could be the cause of that white powdery stuff on my battery? I scraped it off and it just came back. Thanks a lot for any help.

that white powery substance your talking about is most likely battery acid that had leaked some how as to your  ground problem im sry i cant help ne there.Quad L Handyman services

I dont know if this will help but baking soda and water will remove ALL the residue from your battery.  Just start with like 75% soda and 25% water and work it down pouring and scraping and that will fix that.  As for ur actual problem, if it's not related to the corrosion then I dunno.. but thats a start...-Sigi Deba

you may want to try a diff. battery in it mason.  If you are getting corrosion on your terminals, you may have a cell going bad in your battery and that could lead to noise.  If that is the case the car wash was just a coincidence b/c that really could have happed at any time.  Just go by auto zone or pep boys or advance auto parts and get em to test your battery and maybe just stick one out of another car in there just to see.