C46400 Naval Brass: Corrosion Resistance for Marine Fittings
C46400 naval brass is a copper-zinc-tin alloy used for marine fittings, valve components, fasteners, condenser parts, and other equipment exposed to seawater or coastal conditions. Its tin content improves corrosion resistance compared with standard brasses, while its strength and hot-working characteristics support demanding marine applications.
However, C46400 is not suitable for every seawater system. Flow velocity, water chemistry, mechanical loading, manufacturing method, and galvanic compatibility should all be considered before specifying it.
This guide explains the alloy’s composition, specifications, applications, manufacturing considerations, sourcing requirements, and practical limitations.
Why Does Tin Improve C46400’s Marine Performance?
C46400 is a wrought naval brass with the following chemical composition, according to the Copper Development Association:
| Element | C46400 Range |
| Copper | 59.0–62.0% |
| Tin | 0.50–1.00% |
| Lead | 0.20% maximum |
| Iron | 0.10% maximum |
| Zinc | Remainder |
Tin helps reduce dezincification
Dezincification is a form of selective corrosion in which zinc is removed from brass, leaving a porous copper-rich structure with reduced mechanical strength.
The addition of tin improves C46400’s resistance to this process, making it more suitable for marine exposure than unstabilised high-zinc brasses.
Its performance still depends on:
- Water temperature and chemistry
- Flow velocity
- Oxygen and sulphide levels
- Mechanical stress
- Surface condition
- Contact with dissimilar metals
C46400 should therefore be selected according to the complete operating environment rather than its alloy name alone.
How much tin does C46400 contain?
C46400 contains 0.50–1.00% tin by weight, with copper at 59.0–62.0% and zinc making up most of the balance. The mill certificate should confirm that the supplied heat falls within these limits.
Which Specifications Apply to C46400 Naval Brass?
The correct material specification depends on the purchased product form.
| Product Form | Common Specification | Typical Use |
| Rod, bar, and shapes | ASTM B21/B21M | Machined fittings, stems, shafts, and hardware |
| Hot-forging material | ASTM B124/B124M | Forged valve and fitting components |
| Plate and sheet | Applicable specification stated on the drawing | Condenser plates, baffles, and fabricated components |
The drawing and purchase order should state:
- UNS alloy designation
- Applicable material specification
- Product form
- Temper
- Dimensions and tolerances
- Required mechanical properties
- Testing requirements
- Certification and traceability requirements
Avoid specifying only “naval brass,” as this may not provide enough information to control the exact alloy, form, and condition supplied.
How does temper affect C46400?
Temper describes the material condition created through cold working or thermal processing. It can affect:
- Tensile and yield strength
- Ductility
- Machining behaviour
- Formability
- Dimensional stability
The selected temper should match the manufacturing process and final component requirements. A harder condition may provide greater strength but less formability.
Where Is C46400 Naval Brass Used?
C46400 is generally selected for components requiring a combination of corrosion resistance, strength, formability, and reliable manufacturing performance.
Common applications include:
- Marine valve stems and internal components
- Fittings and couplings
- Fasteners and lock pins
- Propeller-shaft components
- Condenser and heat-exchanger parts
- Tube sheets and baffle plates
- Marine hardware
- Bushings and wear components
- Coastal architectural hardware
Valves and fittings benefit from marine corrosion resistance
Valve and fitting components may be exposed to seawater, salt spray, condensation, and marine atmospheres. C46400 offers better resistance to these conditions than standard free-machining brass while retaining useful machining and hot-working characteristics.
The selected material must also suit the component’s:
- Pressure rating
- Wall thickness
- Joining method
- Operating temperature
- Flow conditions
- Required service life
Heat exchangers require careful material matching
C46400 may be used in heat-exchanger and condenser components where both strength and moderate thermal conductivity are required.
Naval brass has lower thermal conductivity than some standard brass alloys because of its tin and zinc content, but it offers improved mechanical strength and marine corrosion performance. Align Manufacturing’s article on brass thermal conductivity in heat exchangers provides a wider comparison of heat-transfer brass grades.
Is C46400 Suitable for Potable-Water Components?
C46400 has a maximum specified lead content of 0.20%. However, the lead percentage of the brass body alone does not prove that a finished product complies with potable-water requirements.
A finished component may also contain:
- Solder or brazing filler
- Plating
- Coatings
- Seals
- Thread compounds
- Other wetted metal parts
The complete product must therefore be assessed against the applicable weighted-average lead and certification requirements.
Where potable-water compliance is required, C46400 should be compared with dedicated low-lead alternatives rather than selected only from its nominal composition. Align Manufacturing’s guide to lead-free brass standards for manufacturing explains the relationship between alloy selection, production controls, and finished-product compliance.
How Does C46400 Compare With C36000 Brass?
| Property | C46400 Naval Brass | C36000 Free-Machining Brass |
| Primary advantage | Marine corrosion resistance | High-speed machining |
| Tin | 0.50–1.00% | Not intentionally added |
| Lead | 0.20% maximum | Approximately 2.5–3.7% |
| Machinability | About 30% of C36000 | Industry benchmark |
| Typical use | Marine and corrosion-exposed hardware | High-volume machined components |
C46400 and C36000 are designed for different priorities.C36000 prioritises machining efficiency
C36000 contains lead that assists chip breaking and reduces cutting friction. It is widely used when fast machining, good surface finish, and economical production are the main priorities.
It should not be substituted for C46400 in a marine application without a proper corrosion assessment.
C46400 prioritises marine performance
C46400 sacrifices machining speed in exchange for improved resistance to marine exposure. It may be more suitable for products exposed to:
- Seawater
- Brackish water
- Coastal spray
- Condensation
- Marine atmospheres
For a broader comparison of C36000, C46400, C48500, and other grades, refer to Align Manufacturing’s brass alloy guide for machining.
The final decision should consider material cost, machining time, expected service life, maintenance, and replacement risk.
When Should Another Marine Alloy Be Considered?
C46400 occupies a useful middle ground, but more demanding applications may require another copper alloy.
Aluminium bronze provides greater strength
Aluminium bronze may be more appropriate for highly loaded components, wear surfaces, propellers, or critical subsea equipment requiring greater strength and resistance to cavitation.
Align Manufacturing’s brass versus bronze material-selection guide compares the mechanical, corrosion, wear, and manufacturing characteristics of both alloy families.
Copper-nickel suits demanding seawater flow
Copper-nickel alloys are widely used for seawater piping, tube bundles, and cooling systems where uniform corrosion behaviour and resistance to flowing seawater are important.
Stainless steel may suit specific requirements
Selected stainless steel grades may provide greater strength or resistance to particular chemicals. However, chloride exposure, crevice conditions, and galvanic coupling still require careful evaluation.
For cast components, material selection should also reflect the process used to form the part. Align Manufacturing’s overview of investment casting materials explains how strength, corrosion resistance, castability, and finishing requirements affect alloy choice.
How Is C46400 Machined and Formed?
C46400 can be machined using conventional equipment, but it does not cut as quickly as free-machining C36000.
Machining parameters should be validated
Tooling and cutting conditions depend on:
- Product form and temper
- Component geometry
- Machine rigidity
- Tool material and coating
- Cutting depth
- Coolant strategy
- Surface-finish requirements
C46400 has a machinability rating of approximately 30% relative to C36000. It can also present work-hardening, galling, chip-control, and surface-finish risks when cutting conditions are poorly controlled.
Align Manufacturing’s article on brass PFMEA for CNC machining explains how alloy properties can be connected to tooling, dimensional, and machining-process risks.
Hot forming can reduce machining
Where the geometry and production volume justify it, hot forging can create a near-net shape before machining. This may reduce:
- Material waste
- Machining time
- Deep-pocket cutting
- Tool consumption
- Overall production cost
Tool design, forming temperature, material flow, trimming allowance, and final machining stock should be validated for the specific component.
Align Manufacturing’s guide to forging fundamentals provides additional context on material flow, grain structure, tooling, and near-net-shape manufacturing.
Casting may suit larger or more complex geometries
C46400 is primarily identified as a wrought alloy, so buyers should not assume that the same UNS designation is suitable for every casting process.
Where a complex marine part is produced as a casting, the engineering team should select an appropriate cast copper alloy and define:
- Alloy specification
- Casting process
- Pressure-integrity requirements
- Porosity acceptance
- Machining allowance
- Testing
- Heat and lot traceability
Buyers assessing regional foundry options can review Align Manufacturing’s overview of Sand casting in Thailand for additional process and sourcing context.
Joining requires control of zinc and filler materials
C46400 may be joined using suitable soldering or brazing processes. Welding requires greater care because zinc loss and porosity can affect joint quality.
The joining process should be supported by:
- Approved procedures
- Compatible filler materials
- Controlled heat input
- Qualified operators
- Inspection requirements
- Corrosion assessment
Surface treatments must also suit the alloy and marine environment. Align Manufacturing’s guide to brass surface finishes explains how polishing, plating, coating, and other treatments affect appearance, corrosion behaviour, and durability.
For complete assemblies involving cutting, forming, joining, machining, and finishing, experienced Metal Fabrication Thailand capabilities can help buyers assess the full production route rather than the raw alloy alone.
What Should Buyers Check When Sourcing C46400?
The purchase specification should state UNS C46400 together with the material standard relevant to the supplied product form.
Review the mill test report
The mill test report should include:
- Heat or lot number
- Copper content
- Tin content
- Lead content
- Iron content
- Zinc balance
- Mechanical properties where required
- Product form and temper
- Applicable material specification
- Manufacturer and testing location
The reported chemistry should remain within the specified C46400 limits.
Confirm material traceability
Traceability should continue from incoming material through finished production using:
- Material identification
- Cutting records
- Batch or work-order numbers
- Forming and machining records
- Inspection reports
- Final certification
- Packaging and shipment documents
Align Manufacturing’s guide to manufacturing documentation control and material traceability explains how drawings, material records, inspection results, revisions, and production evidence can be maintained as one controlled record.
Define the RFQ clearly
For custom components, the RFQ should identify:
- Alloy and material standard
- Drawing revision
- Annual and batch volumes
- Critical dimensions
- Surface finish
- Testing requirements
- Certification documents
- Machining allowances
- Packaging requirements
- Change-control expectations
Align Manufacturing’s guide to ordering custom castings provides a useful framework for preparing drawings, specifications, testing requirements, and supplier documentation before tooling begins.
Audit outsourced operations
Buyers should identify whether forging, machining, plating, heat treatment, testing, or assembly is performed by sub-suppliers.
Supplier qualification should review:
- Process capability
- Inspection equipment
- Material segregation
- Calibration
- Non-conformance controls
- Change management
- Document retention
What Are the Limitations of C46400?
C46400 should not be treated as a universal solution for every marine environment.
High flow can cause erosion-corrosion
Elevated water velocity, turbulence, entrained solids, and poor component geometry can remove protective surface films faster than they reform.
Pumps, elbows, restrictions, valve seats, and tube entrances deserve particular attention.
Ammonia can create cracking risk
Copper alloys can be vulnerable to stress-corrosion cracking in environments containing ammonia or related compounds, particularly when tensile stress is present.
The actual chemical environment should be reviewed before C46400 is used in systems containing ammonia or amines.
Polluted water may behave differently
Sulphides, biological activity, suspended solids, and low-oxygen conditions can change the corrosion behaviour of copper alloys.
Material selection should be based on representative water chemistry whenever the system handles polluted harbour water, industrial discharge, or stagnant seawater.
Dissimilar metals can create galvanic corrosion
Connecting C46400 directly to stainless steel, aluminium bronze, carbon steel, or other metals can create a galvanic couple.
The risk depends on:
- Relative surface areas
- Electrical contact
- Electrolyte conductivity
- Flow conditions
- Coatings
- Cathodic protection
- Position in the galvanic series
Insulating gaskets, sleeves, coatings, or compatible transition components may be needed.
Is C46400 Worth the Additional Cost?
C46400 may cost more to purchase and machine than standard brass, but the correct comparison should be based on total cost of ownership.
Its corrosion resistance can reduce:
- Premature replacement
- Unplanned shutdowns
- Leakage
- Emergency maintenance
- Labour and dry-docking costs
- Damage to surrounding equipment
The economic case is strongest when the component is:
- Difficult to access
- Expensive to replace
- Continuously exposed to seawater
- Safety-critical
- Required to remain in service for many years
For decorative, freshwater, or non-corrosive applications, a less specialised brass may be more economical.
How Should C46400 Be Specified on a Drawing?
A complete drawing note should identify:
- UNS C46400
- Applicable material specification
- Product form
- Temper
- Required dimensions and tolerances
- Mechanical-property requirements
- Chemical certification requirements
- Heat or lot traceability
- Inspection and testing requirements
- Surface finish and joining requirements
The specification should also identify restrictions on material substitution, manufacturing location, sub-suppliers, and process changes.
Align Manufacturing’s main brass manufacturing overview provides additional guidance on matching brass grades with machining, forming, forging, finishing, inspection, and production-documentation requirements.
Conclusion
At Align Manufacturing, we manufacture precision metal components for marine, industrial, oil and gas, railway, construction, and heavy-equipment applications through casting, forging, CNC machining, stamping, and metal fabrication. For marine brass parts, we focus on matching the alloy and product form to the actual corrosion environment, mechanical requirements, and production route. We also support material verification, process control, inspection, and traceable documentation so that C46400 components are manufactured to the required specification rather than selected by alloy name alone.
FAQ
What is C46400 naval brass?
C46400 is a wrought copper-zinc-tin alloy containing 59.0–62.0% copper and 0.50–1.00% tin, with zinc making up most of the balance.
Why is C46400 used in marine applications?
Its tin content improves resistance to dezincification and marine corrosion compared with standard high-zinc brasses.
Is C46400 completely resistant to seawater corrosion?
No. Its performance can still be affected by high flow velocity, polluted water, ammonia, mechanical stress, and galvanic contact with other metals.
What specification covers C46400 rod and bar?
ASTM B21/B21M is commonly used for naval brass rod, bar, and shapes.
Can C46400 be hot forged?
Yes. Material intended for hot forging should be purchased under the applicable product specification and supplied in a suitable condition.
Is C46400 lead-free?
Its specified lead content is 0.20% maximum, but the finished product must still meet the applicable weighted-average lead and certification requirements before being marketed for covered potable-water use.
Is C46400 easier to machine than C36000?
No. C36000 is designed for high machinability, while C46400 is selected primarily for improved marine corrosion resistance.
What should be checked on a C46400 mill certificate?
Confirm the heat number, alloy designation, chemical composition, applicable material standard, product form, temper, required mechanical properties, and complete traceability.
