Yeah, down here most water pipes (old ones, that is) are made of galvanized (zinc plated) steel. And back in the day that sort of process was not a high quality one... the plating always flaked off. So many old buildings down here have leak problems.
Today, most houses are built using PVC pipe instead (although galvanized steel piping is of a much higher quality now), which I don't like either, because people tend to use the thin-walled glue-together type, instead of the threaded thick-schedule one. It breaks easily (for my taste) and is affected by the sun's UV when installed outdoors. Manufacturers say that they come with a UV protective coating, but I've seen those pipes being affected after only 5 years of laying in the sun.

Yes. You are dealing with bad materials, ignorance, and bad decisions. There does exist, "self passivating" steel. When it starts to rust, the first coating of rust becomes the protective layer. There also exists CPVC or PVDC which is gray and survives sunlight. The thin stuff is called, DWV which means Drain, Waste, and Vent. It is not designed to survive any pressure. You can complain about the people cheating on materials for installation or rejoice about the money you get paid for fixing it.

 

There does exist, "self passivating" steel. When it starts to rust, the first coating of rust becomes the protective layer.

Shame on me... I know that aluminum has that property, in which its superficial layer of rust is impermeable to oxygen and protects the material underneath. But I've been an engineer for more than 25 years and it's the first time I've heard of "self-passivating" steel, which is not formally stainless steel.

Does it contain nickel and/or chrome? Is there a specific alloy that you're referring to?

 

You caught me reporting something I heard from a structural engineer. I don't know how self passivatng steel is made, but I know the 3/4 inch galvanized iron pipe to my house was installed in 1959 and it still doesn't leak. What kind of steel with a thickness of about 1/8th of an inch can stay submerged in moving water for 57 years and not dissolve completely? If it isn't self-passivating, that's some incredibly good zinc plating!

 

The Daley Center in Chicago was made with self-passivating steel. It rusted up quickly and that's it.

 

You caught me reporting something I heard from a structural engineer. I don't know how self passivatng steel is made, but I know the 3/4 inch galvanized iron pipe to my house was installed in 1959 and it still doesn't leak. What kind of steel with a thickness of about 1/8th of an inch can stay submerged in moving water for 57 years and not dissolve completely? If it isn't self-passivating, that's some incredibly good zinc plating!

Yeah... and on the other hand, one has to consider that ordinary drinking water not only has dissolved oxygen in it, but a basic amount of chlorine in it too, which is a very aggressive oxidant.

 

Maybe @MaxHeadRoom could enlighten us regarding that self-passivating alloy that you're referring to.

 

Think you guys a talking about "cor-ten" steel. Never heard of being used as water pipes though. They laid a new water main up my street and through my property about 20 years ago, it was cast iron spigot jointed pipe. The one it replaced was about 100 years old and made of the same pipe.
http://www.centralsteelservice.com/cor-ten.htm

Most water districts add phosphates to the water to prevent corrosion of the inside of the pipes. This is what caused Flint, Michigan's water problems, the state/city decided not to use it, to save money.
https://www.cityofflint.com/2015/12/10/flint-increases-corrosion-control-in-water/