Which Boundary?
Lining only, complete pad or shell, all oil-wetted parts, or every component exposed to process gas?
Copper-Free Whitemetal Bearings
Define the chemistry, component boundary and verification method before using this material description.
Copper-Free Whitemetal Is Not a Universal Alloy Grade
The phrase normally communicates a chemical restriction, not a complete bearing specification. It may refer only to the lining or to every component exposed to a process fluid. The drawing or purchase specification must therefore define the alloy chemistry, maximum residual copper, backing and bond materials, scope boundary and acceptance test.
For a strict copper-free application, conventional Babbitt may be disallowed entirely. Do not assume that a low-copper or proprietary whitemetal automatically satisfies the process-material requirement.
Definition
Four Questions Hidden Inside "Copper-Free"
A technically useful specification answers all four before material is purchased or cast.
What Limit?
No intentional addition is not a test limit. State maximum copper by mass and how residual content is treated.
Which Chemistry?
Specify every principal alloying element and impurity limit, not copper alone.
How Verified?
Define certificate, analytical method, sampling location, detection capability and acceptance authority.
Conventional Babbitt
Why Copper Is Normally Present
Soft tin-rich matrix
SnSbSnSbSnSb
Cu-SnCu-SnCu-SnCu-Sn
Material structure
Copper Is Functional, Not Usually an Accidental Trace
Conventional tin-based Babbitt uses a soft tin-rich matrix with harder intermetallic phases. Copper contributes copper-tin phases that help support load and control the alloy structure, while antimony contributes tin-antimony phases.
Removing or sharply reducing copper changes solidification, microstructure, hardness, fatigue behaviour and casting practice. A copper-free formulation must therefore be qualified as its own bearing alloy rather than treated as standard Babbitt with one ingredient omitted.
Standards do not remove the need for a grade: ASTM B23-20(2025) covers eight commercial Babbitt alloys, while ISO 4381:2011 covers tin casting alloys for multilayer plain bearings. A general reference to either standard does not state the project-specific copper limit or complete bearing construction.
Why It Is Specified
Chemical Compatibility Can Govern the Bearing
Confirm the actual fluid, concentration, water content, temperature and exposure route rather than selecting from the process name alone.
H2S and Sour Gas
Gas entering the lube or seal-oil system can promote sulphide formation and depletion of copper-bearing phases. The result can include deposits, softening, clearance change, overheating and fatigue.
Ammonia Exposure
Ammonia service can restrict copper alloys. The requirement may apply more strongly to a copper-alloy backing, carrier or fitting than to the running layer alone.
Contaminated Oil
Water, acidic oxidation products and decomposed additives can attack lead- or copper-containing bearing systems. Oil chemistry must be investigated with the material.
Plant Material Rules
A purchaser may prohibit copper for process safety, product purity or common-material control even where no previous bearing corrosion has occurred.
H2S Attack
Material Change Must Follow Root-Cause Control
IngressProcess gas crosses a seal or oil-system boundary
TransportContaminated lubricant reaches the bearing surface
ReactionSulphide products form and alloy phases are depleted
DistressDeposits, softening, heat, extrusion or fatigue develop
What Copper Removal Can Address
- One susceptible phase in the bearing material system
- Repeated copper-sulphide formation in a confirmed mechanism
- A defined plant or process-material prohibition
What It Does Not Address
- The failed seal or contamination route
- Attack on other alloy constituents, backing or system components
- Oil degradation, water ingress or additive incompatibility
- Incorrect clearance, load, temperature or lubrication
Complete Bearing Boundary
A Copper-Free Lining Is Not a Copper-Free Assembly
Running Layer
Whitemetal, overlay, aluminium-tin, polymer or another qualified surface.
Backing and Interlayer
Steel, bronze, copper-chrome, CCZ, bond coat, plating and diffusion layers.
Mechanical Parts
Pivot, pad support, equalising system, carrier, base ring, dowels, plugs and fasteners.
Oil-System Parts
Nozzles, tubing, coolers, fittings, instrument pockets and any exposed brazing alloy.
Instrumentation
Sensor sheath and installation hardware; electrical conductors may require a clearly defined exception.
Coatings and Repairs
Plating can isolate a substrate but does not make the underlying component copper-free. Damage tolerance matters.
Separate Requirements
Copper-Free Does Not Mean Lead-Free
Cu
Copper-Free
Restricts copper for chemical compatibility, process control or another stated reason.
Pb
Lead-Free
Restricts lead for environmental, occupational, product or regulatory requirements.
Cd
Cadmium-Free
Restricts cadmium because of toxicity and regulatory controls.
One requirement does not imply either of the others. State each element, maximum permitted concentration and test basis separately.
Specification Checklist
Turn the Phrase Into Measurable Requirements
- 1
Define the Exposure
Name the fluid, all constituents and trace contaminants, water content, concentration, pressure, temperature and normal or upset exposure.
- 2
Draw the Boundary
Identify every in-scope component and surface, including lining, backing, interlayers, pivots, fittings, coatings and permitted exceptions.
- 3
Set the Chemistry
State the complete alloy composition and a numerical maximum for copper and every other restricted or controlled element.
- 4
Retain Bearing Performance
Define strength, hardness, fatigue, temperature, bond, lining thickness, finish and hydrodynamic performance requirements.
- 5
Define Verification
Specify certificate level, heat or batch traceability, analytical method, sampling plan, detection limit and retest or rejection rules.
- 6
Control Production
Prevent cross-contamination in melting, casting, tooling and finishing, then identify the approved material on drawings and spares.
Verification and Failure Analysis
Use Evidence, Not Colour or Trade Name
Material Records
Review the approved drawing, supplier specification, heat number and certificate. A trade name must resolve to controlled composition and revision data.
Chemical Analysis
Use a method capable of measuring the specified limit. Handheld XRF can be useful for screening but may not prove a low residual threshold or thin-layer chemistry.
Deposit Analysis
Retain deposits and use SEM/EDS or suitable laboratory analysis to distinguish copper sulphide, tin oxide and other corrosion or contamination products.
System Evidence
Preserve oil, filter debris, seal history, gas analysis, water content, acidity, temperature and operating trends before cleaning the bearing.
Common Questions
Copper-Free Whitemetal FAQ
Is standard Babbitt copper-free?
Not generally. Conventional high-tin grades commonly contain intentionally added copper. Confirm the exact alloy grade and certified analysis.
Does "no intentional copper" prove compliance?
No. It does not establish a residual limit, analytical method or detection capability. Use a numerical acceptance value.
Does copper-free also mean lead-free?
No. Copper, lead and cadmium restrictions are independent and must each be specified.
Will copper-free material stop H2S failures?
It may remove one susceptible phase, but the ingress path, oil condition and compatibility of every other material must still be corrected.
Can a CCZ-backed pad be copper-free?
No. Copper-chrome-zirconium is a copper alloy. A coating may isolate it where permitted, but does not remove copper from the assembly.
Can Oiltech manufacture to a customer specification?
Oiltech can review a defined alloy and bearing specification against the design, manufacturing, inspection and traceability requirements before confirming feasibility.
Technical Basis
The guidance was cross-checked against Waukesha Bearings' bearing corrosion guidance, its paper on fluid-film bearing fundamentals and failure analysis and its aluminium-tin bearing guidance; Mitsubishi Heavy Industries' ammonia-service thrust-pad case; ASTM B23-20(2025); and ISO 4381:2011. The alloy and construction must be approved for the actual machine and process exposure.
Need to Review a Copper-Free Bearing Requirement?
Send the process-fluid data, material restriction, bearing drawing, operating conditions and any corrosion evidence for an engineering review.