Can you guys refresh my memory on this cross connection?
I know that when you connect the two together you will usually get corrosion and/or rust as seen here. House was built in 1972 main line coming in is copper as you can see and the rest of the home galv.
Galvanic reaction - simply, Galvy + oxygen will slowly corrode the copper eventually resulting in a leak.
That appears to be a dielectric union. The orange ring gives it away.
http://www.plumbingstore.com/images/di-electric-fitting-fipsxswt.jpg
There appears to be a dielectic coupling at the connection, which should prevent the corrosion. The dielectric coupling may be damaged (e.g. if it was tightened too much) or there could be copper to galvanized steel contact somewhere else.
Thanks guys I love the message board
That appears to be surface rust on the outside of that dielectric union, not corrosion caused by the connection of dissimilar metals.
And the proper term would not be a cross connection. That occurs when you have the possibility of wastwater and supply water mixing. This is simply a connection of dissimilar metals (that the dielectric should take care of). 
thanks for the clarification (i knew that but my inner brain said right it anyway)
Really soes look like surface rust due to atmosphere. Electralysis hasn’t started. You can tell if electralysis is occuring, because the corrosion will be white or gray (usually depending on the amount of salt in air). See if I can find the thread where this horse was beat long after it died.
http://www.nachi.org/forum/showthread.php?t=24478
This is not the one I was thinking of, but it might help.