Piping Material Selection - Piping Material List with ASTM Grades

Material selection

Material selection is an optimization process. Material selection shall be optimized, considering capital cost and operational costs, and minimizing the overall Life Cycle Costs while providing acceptable levels of safety and reliability. The following key factors apply to materials selection:

• Easy availability of materials
• Suitability for the design life taking into consideration the corrosion allowance
• Compatibility of material with the process fluid
• Suitability of the material for the design temperature and pressure and cyclic loading
• Suitability of materials for the environmental conditions (e.g saline corrosive environment may render some materials ineffective though the material may be compatible with the process fluid)
• Potential ultraviolet degradation of the materials
• Feasibility of providing economical supporting arrangement
• Past experience with material for similar applications
• Additional requirements for corrosion protection such as cathodic protection, chemical injection, inspection, corrosion monitoring and any environmental impact due their implementation
• Weight reduction.
• Fabrication, Inspection and Installation Costs
• Evaluation of failure probabilities, failure modes and consequences

Approach to Material Selection

The sequence of material selection depicted below applies predominantly to oil and gas industry. The basis of material selection uses progressively more expensive material options and is as follows:

1. Use bare carbon steel material i.e. without any internal coating with a corrosion allowance.
2. Use bare carbon steel with corrosion inhibition.
3. Use carbon steel pipe with internal coating or lining.
4. Use carbon steel with cathodic protection.
5. Use Corrosion Resistant Alloy (CRA).

Both metallic and non-metallic materials are used in piping systems. Metallic materials can be classified into two broad categories:

• Ferrous Piping
  • Carbon Steel
  • Stainless Steel
  • Duplex Steel
  • Cast Iron
  • Ductile Iron
• Non-Ferrous Piping
  • Copper
  • Copper Nickel
  • Inconel 625
  • Titanium
  • Aluminium

Carbon and low alloy steels are routinely specified for chemical, petrochemical, paper, oil production and gas processing equipment for sweet and sour service provided the general and pitting corrosion can be maintained within acceptable bounds and the materials are resistant to sulfide stress cracking. Carbon steel with adequate corrosion allowance is suitable for many applications and performs satisfactorily at temperatures between -29°C and 427°C. If the predicted corrosion rates of carbon steel are not sustainable for the design life of the plant facilities considering an acceptable corrosion allowance, an active means of protection of carbon steel must be considered. In most cases a corrosion allowance of 3 mm is considered appropriate to meet the design life for carbon steel material. In many engineering organizations a 6 mm corrosion allowance is considered as the upper limit of corrosion allowance.

Low-temperature carbon steel is used for subzero temperatures and low-alloy carbon steel is used for high temperature applications. After carbon steel, stainless steel can be used for many corrosive service applications followed by duplex steels and other corrosion resistant alloys such as Inconel 625 and Incoloy 825. Metallurgist or Corrosion Engineer is in most organizations responsible for preparation of material selection philosophy, material selection report and material selection diagrams. The material selection report and material selection diagram forms the basis for developing the piping material classes. 

ASME B31.3 lists the commonly used metallic piping materials. Table below lists the various ASTM codes for Ferrrous and Non-Ferrous materials used in plant facilities.

List of ASTM Codes for Piping Materials - Ferrous Materials

List of ASTM Codes for Piping Materials - Non-Ferrous Materials