Corrosion or not?

[psklein578]

I was not aware that I had a problem until today when I looked behind the water heater and saw what’s in the picture. Definitely a seeping leak. Could that be caused by corrosion between the brass valve and the copper pipe? If it is, what can I do about it?

 

[MicEd69]

You need to clean that corrosion material off the be sure, but I'm betting that there is a material there that is causing some pretty good galvanic corrosion to the brass valve, or that just looks like a brass valve.