Condensation on water supply lines

I am wondering if anyone has seen this and can tell me what could be the cause of it. I recently inspected an older home, approximately 110 years old. In the basement - which has many issues - I came across a lot of condensation on one of the water lines running across the ceiling. Most of the water lines are copper but this material is different, it looks like black iron pipe but could be something different. It has condensation formed along the entire length of it. Any ideas why?





Looks like it might be galvanized steel. And the condensation is usually warm moist air condensing on a cold surface - wet basement? Those masonry walls typically allow plenty of moisture into the basement.

look up condensation, dew point temperature etc.

Condensation commonly occurs when a vapor is cooled to its dew point, but the dew point can also be reached through compression. The condensed vapor is called a condensate, the laboratory or the industrial equipment used for condensation is called a condenser.
The science of studying the thermodynamic properties of moist air and the interrelationships between these in order to analyze, and predict properties by changing in the conditions of moist air is called psychrometry. The interrelationship can be graphically represented, and prediction carried out graphically by the psychrometric chart. Most people think the water is condensation, but condensation is only the process of change.
Water vapor that naturally condenses on cold surfaces into liquid water is called dew. Water vapor will normally only condense onto another surface when the temperature of that surface is cooler than the temperature of water vapor.

The dew point is the temperature to which a given parcel of air must be cooled, at constant barometric pressure, for water vapor to condense into water. The condensed water is called dew. The dew point is a saturation point.
The dew point is associated with relative humidity. A high relative humidity indicates that the dew point is closer to the current air temperature. Relative humidity of 100% indicates the dew point is equal to the current temperature and the air is maximally saturated with water. When the dew point remains constant and temperature increases, relative humidity will decrease.[1]
At a given barometric pressure, independent of temperature, the dew point indicates the mole fraction of water vapor in the air, and therefore determines the specific humidity of the air. The dew point is an important statistic for general aviation pilots, as it is used to calculate the likelihood of carburetor icing and fog, and estimate the height of the cloud base.

what is the temperature of the incoming water?

What is the relative humidity in the space?

How to repair it; learn how to use a psychrometric chart.

Thanks, I realized it was condensation formed by temperature difference. I guess what I was looking for was why on this pipe and not on the copper lines attached to it as well?

I can see water drops on the copper side too.
Just write up lack of Dielectric fitting.