Carbon Steel, Stainless Steel, and Brass Fittings: Compatibility and Limits

The material used for tube fittings and adapters matters because it affects pressure capability, corrosion resistance, temperature range, contamination risk, and service life.

Hydraulic fittings are commonly made from carbon steel, stainless steel, or brass. The best choice depends on the equipment, environment, fluid, and connection method.

Carbon Steel Fittings

Carbon steel fittings are widely used in industrial, construction, and agricultural equipment. Some carbon steel fittings can handle more than 5,000 psi, so they can fit both lower-pressure and higher-pressure systems when the exact product rating supports it.

The limitation is environment and forming behavior. Carbon steel can be more brittle under severe force, which makes it a poor choice for some crimping applications. It also needs an appropriate protective coating, such as zinc or another approved finish, when rust is a concern.

Stainless Steel Fittings

Stainless steel is often selected where carbon steel could corrode, rust, or contaminate the process. It is common in food processing, pharmaceutical manufacturing, textile applications, chemical service, marine exposure, and other corrosive environments.

Stainless fittings usually cost more than carbon steel, but they can provide the strength and durability needed in harsher service. Many stainless fittings are rated around 10,000 psi, and specially designed stainless products may be rated as high as 20,000 psi.

Where Stainless Steel Is Common

Stainless steel can be useful in oil and gas equipment, offshore service, chemical processing, food manufacturing, medical and instrumentation systems, agricultural fertilizer equipment, and marine applications.

Those environments often combine pressure, corrosion, cleaning chemicals, moisture, or salt exposure. Material compatibility should be checked before assuming a stainless fitting is interchangeable with another material.

Brass Fittings

Brass fittings provide moderate strength and good ductility at elevated temperatures, but they are normally used in lower-pressure applications than stainless steel. Many brass fittings are used around pressure classes up to about 3,000 psi, depending on design.

Brass is also not generally recommended above about 400 F. In hydraulic and industrial work, that temperature limit should be checked with the fitting design, seal material, and fluid exposure.

Choosing the Material

A fitting material should be selected with the full transfer line in mind. Tube or hose size, system pressure, fluid compatibility, temperature, corrosion exposure, crimping method, and maintenance conditions all matter.

Stainless steel and brass can both be useful, but they are not universal substitutes. Confirm the material, pressure rating, coating, and environment before replacing one fitting material with another.