If black pipe is not welded properly, it can embrittle connections and even be dangerous.
As with many things in life, the details are important when welding black pipe.
So, a simple yes or no is not enough to answer this question properly. Depending on the materials and welding process, the answer will vary.
What is Black Pipe?
The industry uses “black pipe” as a term to differentiate between plain mild steel and galvanized pipe. So, black pipe is generally any ungalvanized steel pipe.
Black pipe is sometimes called black steel pipe, black iron pipe, and industrial pipe. As already indicated, welding is possible since this product is made from mild steel.
But because of the various names used, some mistake black pipe for iron and wrongly assume that welding is difficult.
Also, black pipe works well for a number of uses. It is commonly used as supply lines to carry compressed air, natural gas, propane, and steam.
You will also see it used as supply lines in sprinkler systems.
Welding Black Pipe
So, we already know you can weld black steel pipe. But what welding processes should you use?
Well, you can employ any of your favorite methods that work for mild steel. Most welders have a preferred method, including the most common welding methods like stick, MIG, flux core, and TIG welding.
To state the obvious, you should utilize good preparation and cleaning procedures. It not only minimizes fumes and smoke, but it makes for a better weld. In most cases, the black oxide layer should be removed with a grinder or wire brush down to bright metal.
Remember, black pipe can also be treated/coated. So, be sure to remove any oil, lacquer, or enamel/tar that may be present as well as dirt and debris.
One last caution, threaded pipe joints may have teflon tape in the joint. In the rare situation where you try to weld an assembled joint, any teflon present will burn and release toxic gases.
Welding threaded joints with teflon should be avoided.
Is it safe to weld?
Black steel pipe is not galvanized, so it is safe to weld. We are not including galvanized steel in this discussion.
Galvanized pipe is not to be welded unless a proper respirator is worn. Welding galvanized steel, will generate zinc oxide fumes which are highly toxic. Chronic exposure can even result in death.
Use Caution Welding Black Pipe Fittings
It is also important to note, some black pipe fittings are difficult to weld. These fittings are made from malleable iron.
When heated over 1700℉, malleable iron transforms. It returns to cast iron, which is brittle and fractures easily.
So, braze or braze weld malleable iron fittings to keep the temperatures low.
An alternative is to use socket weld fittings made from forged steel. These can be welded without fear of embrittling the fitting. You simply weld a steel pipe to a steel fitting with your preferred method of steel to steel welding.
These forged steel fittings are readily available in and come in various sizes.
What is Black Pipe Coated With?
Since black pipe is not protected by galvanizing, the factory creates a stable layer of iron oxide during the manufacturing process. This gives black pipe its distinctive ebony color.
But more importantly, it provides a moderate degree of corrosion protection for the pipe.
The pipe may also be treated/coated with coal tar enamel, lacquer, or oil for added protection. This may add a sheen or glossy appearance to the pipe.
Can You Weld Black Iron Pipe To Steel?
Black iron pipe is simply mild low carbon steel so it can be welded to most grades of steel.
Any limitations will come from the alloys of the other steels as then metallurgical needs such as heat treatments will need to be looked at for the heat-affected zone as well as potential problems such as weld zone cracking and galvanic corrosion issues.
Surface preparation is important when welding “black iron pipe”. By its very nature it has a lot of “stuff” on its surface.
Since it is just a mild low carbon steel it has a lot of forgiving properties that allow you to weld on it with average skill levels.
But if it is going into gas carrying service and not ornamental surface then really pay attention to codes and ticket requirements.