A guide to black carbon steel pipe

Black carbon steel pipe is a common carbon steel pipe in engineering, usually refers to ordinary carbon steel pipe without coating or other surface anti-corrosion treatment, because its surface is covered with a layer of black oxide (rolled or heat treatment formed oxide layer) named.

Basic characteristics of black carbon steel pipe

Material: Mainly low carbon steel (ASTM A53/A106), low carbon content (0.05%~0.25%), easy to weld and process.
Surface condition: There is a black oxide (Fe ₄) on the surface. It is a natural oxide layer after hot rolled or heat treatment. To some extent, it rusts when exposed to moisture for a long time.
Corrosion resistance: Poor corrosion resistance, need to rely on external anti-corrosion measures (such as paint, insulation) or internal anti-corrosion treatment (such as lining, epoxy coating).
Cost: Low price, it is a low-cost substitute for galvanized steel pipe and stainless steel pipe.
Strength and toughness: high compressive strength, but lower ductility than stainless steel and alloy steel pipes.

Manufacturing process

The manufacturing process of black carbon steel pipe is divided into seamless manufacturing and welding manufacturing, seamless manufacturing mainly uses hot rolling and cold rolling process, welding manufacturing is the use of welding process. The steel pipes produced by different manufacturing processes have different characteristics and properties.

Hot rolling process: through high temperature rolling molding, rough surface, often used for low pressure fluid transport.
Cold drawing process: smooth surface after cold processing, high dimensional accuracy, suitable for precision engineering.
Welding process: It is divided into straight seam welded pipe (ERW) or spiral welded pipe (SAW) for different pressure scenarios.

Compared with galvanized steel pipe
The galvanized pipe is sprayed with zinc layer on the surface of the steel pipe, and the method of sacrificial anode is used to improve the anticorrosion ability of the steel pipe. The cost of galvanized steel pipe is higher, suitable for use in medium humidity and general corrosion environment, corrosion resistance is strong, and the average service life is 10-20 years. The cost of the black carbon steel pipe is low, the corresponding anti-corrosion performance is also low, the anti-corrosion performance mainly depends on the external coating, suitable for use in dry or short-term anti-corrosion scenarios, no anti-corrosion measures can generally be used for 5-10 years.

Application field

Gas transmission: Natural gas, liquefied petroleum gas (LPG) pipeline system.
Fire fighting system: Building fire sprinkler pipe (need to withstand high pressure).
Industrial pipeline:
Transport steam, air, oil and other non-corrosive fluids.
Structural support or equipment pipelines for chemical and power industries.
Building structure: temporary scaffolding, building frame (need to be painted to prevent rust).

Anti-corrosion treatment and maintenance

Paint/coating: epoxy resin paint, anti-rust paint, etc., to enhance the oxidation resistance.
Coating protection: Use polyethylene tape or heat shrinkable sleeve to wrap the pipe.
Regular inspection: Rust should be checked regularly in humid or corrosive environments.

Matters needing attention

Do not use for drinking water: black tubes may release rust and pollute water quality.
Welding and cutting: The surface oxide layer should be removed to avoid the quality of the weld.
Environmental restrictions: Use with caution in high humidity, coastal areas, or chemical corrosion environments.

Alternative material

Galvanized steel pipe: moderate cost performance, suitable for general corrosion environment.
Stainless steel pipe (304/316) : high corrosion resistance, but high cost, complex welding process.
Plastic pipe (such as PVC, PP-R) : lightweight corrosion resistance, but limited pressure and temperature resistance.