Choosing the right material is one of the most important decisions in valve specification. Get it right and a valve will perform reliably for years, often decades, in conditions that would destroy a lesser component. Get it wrong and the consequences range from corrosion-driven leakage to unplanned shutdowns and, in the worst cases, safety incidents.
At Colson Valves, we manufacture instrument ball valves, needle valves, check valves, manifold valves and Double Block and Bleed (DBB) valves across a comprehensive range of exotic and corrosion-resistant alloys. This article sets out the materials we work with and why each one is specified for the environments it serves.
Why material selection matters
Standard stainless steel is well suited to many applications, but it has limits. In chloride-rich, sour service, high-pressure, or chemically aggressive environments, conventional grades can corrode, pit, or fail through stress cracking long before the end of their intended service life.
The materials we use are selected to address specific conditions: operating temperature, working pressure, process media, chloride concentration, pH, sour service requirements, and external environment all factor into the decision. Correct specification delivers longer service life, lower maintenance frequency, compliance with industry standards, and reduced risk of leakage and unplanned downtime.
Duplex and Super Duplex stainless steels
Duplex and Super Duplex stainless steels offer approximately twice the yield strength of conventional 316 stainless steel, combined with excellent resistance to chloride-induced corrosion. Their dual-phase microstructure accounts for both properties.
These grades are commonly specified for offshore oil and gas platforms, subsea systems, seawater handling equipment, desalination plants, and chemical processing facilities. Super Duplex grades UNS S32750 and UNS S32760 are particularly well suited to high-chloride environments where resistance to pitting and crevice corrosion is critical.
Colson Valves manufactures instrumentation and Double Block and Bleed (DBB) valves in both Duplex (ASTM A182 F51 / ASTM A479 UNS S31803) and Super Duplex (ASTM A182 F55 / ASTM A479 UNS S32760; ASTM A182 F53 / ASTM A479 UNS S32750).
6Mo stainless steel
The elevated molybdenum content in 6Mo stainless steel (ASTM A182 F44 / ASTM A479 UNS S31254) gives it markedly better resistance to pitting and crevice corrosion than standard austenitic grades. It is particularly suited to chloride-rich environments and is regularly specified for seawater cooling systems, desalination plants, chemical processing facilities, and pharmaceutical manufacturing.
Monel® 400
Monel® 400 is a nickel-copper alloy with a minimum ultimate tensile strength of approximately 70 ksi and outstanding corrosion resistance in marine, saline, and hydrocarbon environments. It resists seawater corrosion, saltwater spray, hydrofluoric acid, alkalis, and neutral salts. These properties make it a sound choice for offshore platforms, shipbuilding, naval applications, and coastal chemical processing – anywhere long-term exposure to seawater is a primary concern. Colson Valves has supplied Monel® 400 instrumentation valves for offshore and marine projects where reliable performance over an extended service life is essential.
Aluminium Bronze
Aluminium Bronze (NES 833) combines corrosion resistance with good mechanical strength and outstanding resistance to biofouling in seawater service. It also performs well against cavitation and erosion – a meaningful advantage in dynamic marine environments.
Colson Valves has supplied Aluminium Bronze valves to the defence and maritime industries, and the material remains a proven choice for naval vessels, offshore structures, and seawater distribution systems.
Alloy 625
Alloy 625 is a nickel-chromium-molybdenum alloy with a minimum ultimate tensile strength of approximately 100 ksi. It resists Hydrogen Sulphide (H₂S), carbon dioxide, chloride-induced corrosion, pitting, crevice corrosion, and sulphide stress cracking.
The oil and gas industry specifies Alloy 625 extensively for sour gas production, subsea control systems, chemical injection systems, and high-pressure instrumentation. Where the environment is aggressive and the consequences of valve failure are significant, Alloy 625 is a material that performs.
Alloy 825
Alloy 825 is a nickel-iron-chromium alloy with additions of molybdenum and copper, providing strong resistance to both reducing and oxidising acids. It is well established in sour service environments and offers reliable protection against stress corrosion cracking.
Colson Valves has supplied Alloy 825 instrumentation valves for critical oil and gas applications where operational reliability and corrosion resistance are non-negotiable.
Hastelloy® C276
Hastelloy® C276 is among the most versatile corrosion-resistant alloys available. It withstands strong oxidising and reducing agents and performs reliably in chemical processing, waste treatment, acid handling, pollution control, and pharmaceutical manufacturing environments. Where process conditions are particularly aggressive, it is frequently the material of last resort before more exotic options are considered.
Titanium Grade 2
Titanium Grade 2 (ASTM B348 Grade 2 / ASTM B381 Grade 2) is virtually immune to seawater corrosion and highly resistant in oxidising environments. Its high strength-to-weight ratio makes it a useful choice where system weight is a design constraint, including offshore systems, seawater cooling circuits, desalination plants, and aerospace applications.
Other specialist materials
Where standard options do not meet a project’s requirements, Colson Valves can source and manufacture in additional specialist materials including Tantalum. We work with customers at the specification stage to identify the most appropriate solution for the application.
Engineered solutions for demanding environments
We supply valves to the oil and gas, petrochemical, chemical processing, power generation, marine, defence, offshore renewables and desalination sectors. Our experience with exotic alloys means we can provide practical guidance on material selection as well as the manufacturing capability to deliver it.
For technical enquiries or to discuss your project requirements, contact the Colson Valves team.