What would cause just the water pipes to corrode at certain areas?
No moisture noted in basement.
Are the green ones hot?
Chemical reactions tend to accelerate with warmer conditions.
I was looking at that. The furnace humidifier is tied to the lines that are corodded. I thought it was the hot.
Condensation. . .
It looks like excessive flux in some areas as well. . .
What would your recomendation be? Insulate the pipes?
The same home had glavanic corrosion and a leak above the water heater.
I recommended a qualified specialist review the supply piping.
There were 2 receptacles that the kids chalked and I wanted to make sure they were not messing with the plumbing.;
If you have contact between galvanized steel and copper pipe ANYWHERE on the system, you can get that corrosion in a different area. I find that many times if there is contact at one area, most of the corrosion will be near an area where the copper pipe is in contact with the ground or electrically grounded somehow.
It looks like you have steel to copper contact at a duct (?)
Replace all of the pipe hangers for a start.
Good eye Brian
Nice catch Brian. If only the hot is reacting it is a chemical reaction that takes place only at a certain temp. The green (patina) comes from sodium or other salt reacting with the copper. This happens over time with all copper, look at the statue of liberty. In most cases it is not corrosive.
I believe Ralph pointed it out first. I just chimed in after. 
Yeah, for some reason, I never listen to Ralph. 
Like I said, Good eye Brian.
Sorry Ralph.
I was just sharing my personal experience. If I see that type of corrosion, I pretty much always find copper to galvanized steel contact somewhere in the system.
In the posted pictures I did see what looked like copper to galvanized steel contact at some type of sheet metal (second set of pictures).
The other type of corrosion I see is due to excessive flux, but that is typically only near soldered joints.
I haven’t really seen much patina type corrosion on copper which is not exposed to the weather.
Dave
in looking at the first picture in the second set I’d have to ask is there a disconnected dryer vent near by?..the excess of hot moist air would speed along some of what You are seeing imo…jim