Aluminum vs Stainless Steel vs Brass for Rotary Union Bodies
Select body, wetted-part, and seal materials from the medium and environment; no single metal provides the longest life in every rotary-union application.
Body material is only one part of rotary-union durability. The medium may also contact shafts, sleeves, ports, fasteners, and seals, while the exterior faces humidity, washdown chemicals, dust, or salt. A useful material decision separates body, wetted parts, dynamic sealing surfaces, and elastomers instead of treating the product as one metal.
What each common body material offers
Aluminum keeps mass low and is readily machined; surface treatment and the operating environment influence corrosion and wear behavior. Stainless steel is often selected for stronger corrosion resistance or demanding cleaning environments, with greater mass, machining cost, and possible galling considerations. Brass machines well and is used in many air and water components, but compatibility still depends on fluid chemistry, temperature, and connected metals.
None of these descriptions confirms compatibility by itself. Grade, heat treatment, coating, surface finish, mating materials, seal compound, and the exact medium can change the result.
Separate the material decisions
- Body and mounting structure Review mass, stiffness, thread strength, external corrosion, coating durability, and how the union attaches to the machine.
- Wetted and dynamic parts List every material in contact with the medium, including shaft and sealing surfaces, and check chemical and galvanic compatibility.
- Seals and operating condition Match seal compound to medium, pressure, temperature, speed, lubrication, cleanliness, and expected dwell or rotation.
A practical material-selection sequence
- Define the fluids Include concentration, additives, contamination, cleaning agents, temperature range, and whether the system is flushed or left filled.
- Define the environment Record humidity, washdown, salt, abrasive dust, UV exposure, and contact with surrounding machine chemicals.
- Compare the complete material set Review body, shaft, ports, fasteners, coatings, seals, lubricants, and connected piping as one system.
- Validate special service For an unlisted medium or environment, request a material review and agree on test or inspection requirements before production use.
Confirm the selected model’s published body material on its product page. This article does not rank which metal lasts longer in Begapunk testing; grade, coating, seals, and the exact medium can change the result.
Review materials for a specific medium or environment
Send the medium, cleaning chemicals, and the candidate model. We will check the published body material rather than a generic metal preference.