What is the service life of mild steel pipes?

Mild steel pipes, also known as low-carbon steel pipes, refer to pipes made of low-carbon steel, whose carbon content is usually ≤0.25%, and contain a small amount of manganese, silicon, phosphorus, sulfur and other elements. Due to its low carbon content, this type of steel pipe has good plasticity, weldability and processability, and is low in cost. It is widely used in construction, machinery, energy, transportation and other fields.

What is the service life of mild steel pipes?

The service life of mild steel pipes is affected by many factors, and can usually be comprehensively evaluated from the following aspects:

Main influencing factors:

1. Environmental conditions
Dry indoor environment: The service life can reach more than 50 years (such as building structure pipes).
Wet or outdoor environment: It may be shortened to 20-30 years. If exposed to rain, salt spray (coastal areas) or industrial pollution, the corrosion rate will accelerate.
Buried pipelines: Depends on the corrosiveness of the soil (such as pH, resistivity), the service life is generally 15-50 years, and anti-corrosion coating or cathodic protection is required.

2. Anti-corrosion measures

Unprotected bare steel pipes may only last 5-15 years in harsh environments. Galvanizing, epoxy coating or 3PE anti-corrosion can extend the service life to 30-50 years or even longer. 

3. Use stress

Long-term exposure to high loads or fatigue stress (such as fluid pressure fluctuations) may cause metal fatigue and shorten the service life. 

4. Media contact

The transportation of corrosive media (acids, alkalis, seawater) may require stainless steel or plastic lining treatment, otherwise the service life will be greatly reduced. Typical application scenario reference: Building structure (such as scaffolding): Galvanized low-carbon steel pipes can last for more than 30 years in normal climates. Galvanized low-carbon steel pipes combine strength and rust prevention, and the cost is much lower than aluminum alloy. Water supply/gas pipelines: The design life of buried steel pipes with anti-corrosion treatment is usually 30-50 years. Industrial pipelines: High temperature or corrosive environments may require regular replacement (10-20 years). Automobile chassis parts: Use its stamping formability to manufacture non-load-bearing structural parts.

Chemical composition and classification of low carbon steel pipes:

Carbon (C): ≤0.25%    Function: Affects strength and hardness, low carbon steel has good toughness but low strength
Manganese (Mn): 0.30%~0.60%      Function: Improve strength and hardenability
Silicon (Si): ≤0.30%        Function: Enhance strength and oxidation resistance
Phosphorus (P) ≤0.045%      Function: Improve strength but increase cold brittleness
Sulfur (S) ≤0.045%        Function: Reduce weldability and easily cause hot brittleness

Common classification:

By manufacturing process:
Welded steel pipe (such as ERW high frequency welded pipe, submerged arc welded pipe) - low cost, suitable for low pressure fluid transportation.
Seamless steel pipe (hot rolled or cold drawn) - higher strength, used for high pressure, precision mechanical structures

By use:
Structural steel pipes (such as scaffolding, building support)
Fluid transport pipes (such as water, gas, oil pipes)
Tubes for mechanical processing (such as auto parts, agricultural machinery accessories)

Advantages and disadvantages of low carbon steel pipes:

(1) Advantages
Low cost: The smelting process of low-carbon steel is mature, the iron ore resources are abundant, the production process is simple, and the price is much lower than stainless steel or alloy steel pipes.
Easy to process: Good ductility, suitable for stamping, bending, cutting, welding (such as building steel structure), reducing manufacturing and construction costs.
Excellent welding performance: Low-carbon steel is not easy to produce welding cracks and is suitable for various welding methods (arc welding, gas welding, etc.).
High cost performance: In non-extreme environments, the performance is sufficient to meet most needs and is suitable for large-scale applications (such as scaffolding, ordinary pipelines).
Recyclable and environmentally friendly: 100% recyclable, in line with the trend of green manufacturing.

(2) Disadvantages
Low strength: The tensile strength (300-500 MPa) is not as good as medium-high carbon steel or alloy steel.
Poor corrosion resistance: easy to rust, need galvanizing, painting or plastic coating and other anti-corrosion treatment.

Poor high temperature performance: easy to oxidize at high temperature (>300℃) for a long time, and the strength decreases.

How to extend the life of mild steel pipe?
Surface treatment: hot-dip galvanizing, epoxy coating, plastic spraying.
Regular maintenance: check rust and apply anti-rust paint.

Reasonable material selection: stainless steel or plastic-lined composite pipes are used in corrosive environments.

Conclusion:

Mild steel pipe (low carbon steel pipe) is an economical, practical, easy to process, and weldable pipe. It is widely used in construction, machinery and fluid transportation fields, but it should be noted that its corrosion resistance is poor. When selecting, it is necessary to combine the use environment (corrosion, temperature, pressure) to decide whether to adopt protective measures or alternative materials (such as stainless steel pipes).

Read more: Mild Steel Seamless Pipe or Mild Steel ERW Pipe