This may be of help: "The copper pipe green corrosion is caused by the copper being dissolved out of the pipes and then deposited elsewhere. You may also find tiny, pinhole leaks in your pipes as the copper is slowly worn away."

Based on my limited experience, the next thing you will see is pinhole leaks or seepage from that pipe. Plan for a new pipe.

Bruce

@krissie55 @Bruce in Northern Virginia Thanks. Any idea what caused the corrosion ? What should I do for the rest of the piping system thru out the house ?

I don't think you have anything to worry about. It's probably just some surface corrosion. I've seen much worse in my 70 year old house. How old is this piping? Take some 220 grit sandpaper to a small section and see if it cleans off quickly. If it's deeply pitted, it could be a problem. Take a look at it now and then.

Spots of green on copper pipes is an indication of pinhole leaks. Water seeps through small holes and reacts with the outside layer.

My guess is reoccurring condensation from the pattern.

The colored spots are not pin holes in the pipe. The overall pattern is from condensation as previously stated. The coloration at these condensation drops is due to various salts (chlorates, sulfates, nitrates, etc.) present in the dirt around us that gets on the pipes. These salts readily dissolve in water and then react with the copper pipe; it is minor corrosion of the pipe surface. A common copper compound that matches the color shown is copper sulfate.

Thanks all. I tried to removed what's on the surface and this is what I see.

The top portion of the pipe looks much better than the bottom portion in general.

It's condensation. You can ignore it, or you can insulate the pipe.

It's verdigris.

Cold water pipe, warm garage ceiling=condensation.

You can find pipe insulation sleeves at the big box stores.