# UNS C46400 brass

Specifying uninhibited naval brass by chemistry, product form, temper, test basis and marine exposure requirements.

Reviewed: 2026-11-01

Tags: materials, copper-alloys, brass, naval-brass

**C46400** is commonly called **naval brass, uninhibited**.

## Chemistry and product identity

Concast's **H02 C46400 rod** row for **over ½ through 1 in** gives **60 ksi minimum tensile** and **27 ksi minimum yield at 0.5% extension under load**. The **25% minimum elongation** uses four times diameter or specimen thickness. The table cites **ASTM B21/B21M-20**. Use the edition specified on the order. [Concast naval-brass test table](https://www.concast.com/files/C46400.pdf)

Finkelstein Metals' C46400 sheet lists **59.0–62.0% Cu**, **0.5–1.0% tin**, zinc remainder, **0.2% maximum lead** and **0.1% maximum iron**. Thus, an informal 60/40 description omits both the tin addition and the composition limits. “Uninhibited” should also remain in the material description rather than being silently replaced by a claim of dezincification resistance.

The manufacturer separately lists round, hexagonal/octagonal, square and other shapes. Its dimensional offering is not proof that every size and shape has the same mechanical requirements. Confirm the ordered form, condition, standard and certificate. The cited sheet does not show a printed revision date; its upload path is not used as one. [Finkelstein Metals, C46400 product sheet](https://www.finkelstein-metals.com/en/wp-content/uploads/2024/08/Finkelstein-Metals_Product-page_C46400_03.pdf)

Wieland Concast explicitly identifies its C46400 as **continuous cast and drawn**, with **H02 half-hard** stock offerings. The named manufacturing route and finished condition belong together; an application list cannot qualify arbitrary as-cast material or another temper. [Wieland Concast, C46400 sheet](https://www.concast.com/files/C46400.pdf)

## Select the product standard and edition

ASTM's public **B21/B21M-20(2026)** scope concerns naval-brass **rod, bar and shapes** and includes C46400. It directs hot-forging material to **B124/B124M**. A B21 callout therefore should not be assumed to cover every finished forging, plate or pressure component. Identify the required product standard and edition explicitly, including any additional component requirements.

ASTM also states that its inch-pound and SI systems are independent standard systems and must not be combined to establish conformance. Preserve the ordered system when evaluating a certificate. [ASTM, B21/B21M-20(2026) public scope](https://store.astm.org/b0021_b0021m-20r26.html)

## Strength depends on size, temper and test definition

Concast's sheet identifies the following **H02 half-hard rod** requirements as according to **ASTM B21/B21M-20**:

| Rod size interval | Minimum tensile strength | Minimum yield strength | Minimum elongation |
| --- | --- | --- | --- |
| Over 1/2 through 1 inch | 60 ksi / 414 MPa | 27 ksi / 186 MPa | 25% |
| Over 1 through 2 inches | 58 ksi / 400 MPa | 26 ksi / 179 MPa | 25% |
| Over 2 through 3 inches | 54 ksi / 372 MPa | 25 ksi / 172 MPa | 25% |

Its yield heading is **0.5% extension under load**. Its elongation basis is **four times diameter or specimen thickness**. Do not relabel the yield result as 0.2%-offset proof stress or the elongation as a fixed two-inch gauge result. The table's historical standard edition remains part of this example; confirm the requirements of the edition actually ordered. [Concast, C46400 mechanical-property table](https://www.concast.com/files/C46400.pdf)

## Forming, machining and joining

ThyssenKrupp's **2013** copper-and-alloys guide describes C46400 as a duplex alpha-plus-beta brass, with excellent hot workability and fair cold workability. It rates soldering and brazing favorably and gas-shielded arc welding as fair. Its relative machinability rating is **30**, with free-cutting brass assigned **100**. These are process-selection indications, not qualified cutting parameters or joint acceptance criteria. The guide expressly says its information is **not for design or specification purposes**. [ThyssenKrupp Materials NA, Copper and Alloys Guide, C46400](https://ucpcdn.thyssenkrupp.com/_legacy/UCPthyssenkruppBAMXNA/assets.files/tkmna_com/products/collateral/copper-and-alloys-guide.pdf)

Plan the forming and joining sequence around the required final condition. Establish tooling, edge preparation, filler/flux compatibility, cleaning and inspection on the actual geometry. Do not extrapolate a hot-working or annealing range into an approved furnace cycle without the material, section and outcome requirements.

The same guide gives electrical conductivity **26% IACS at 68 °F in the annealed condition**, noting lower conductivity in hard temper. A conductivity entry with a specific temper cannot be transferred to every delivered bar or heated assembly. For thermal or electrical service, retain temperature, condition and geometry in the assessment. [ThyssenKrupp, C46400 physical-property qualifications](https://ucpcdn.thyssenkrupp.com/_legacy/UCPthyssenkruppBAMXNA/assets.files/tkmna_com/products/collateral/copper-and-alloys-guide.pdf)

## Marine resistance is conditional

The Copper Development Association's **Publication 206**, issued **May 2011 and revised December 2012**, explains that approximately 1% tin slows dezincification in alpha and alpha-beta brasses. It uses naval-brass heat-exchanger tubesheets as an example where slow attack in a thick section may permit useful service life. That is not an immunity claim or a universal corrosion allowance.

The same guidance identifies ammonia stress-corrosion cracking as a separate concern requiring an ammonia-bearing environment and tensile stress, with marine atmospheric exposure specifically relevant. Mitigation needs assessment of the actual material condition, loads and environment; no universal stress-relief or cathodic-protection recipe follows from the alloy name. [CDA, Copper Alloys for Marine Environments, brasses](https://www.copper.org/applications/marine/cuni/pdf/pub206.pdf)

For selection, record immersion versus atmospheric exposure, water chemistry, temperature, flow, deposits, cleaning agents and contact with other materials. If a corrosion allowance or inspection interval is required, establish it from qualified service evidence rather than borrowing a rate for another brass or another exposure.

The Canadian Conservation Institute explains that dezincification removes zinc and leaves copper-rich material; severe attack can produce weakness or perforation, while yellow-to-pink discoloration may be an early visible sign. This is different from proving section loss by color. Investigate affected surfaces and underlying metal against the component's acceptance requirements; polishing away discoloration does not restore lost material. [CCI, Preventing and Treating Dezincification of Brass](https://www.canada.ca/en/conservation-institute/services/conservation-preservation-publications/canadian-conservation-institute-notes/dezincification-brass.html)

## Purchase and release requirements

An actionable order states C46400, governing product standard/edition, form, size, tolerances, final temper, surface finish and required inspection documentation. State the required units and mechanical test definitions. For forgings or pressure-retaining parts, add the applicable manufacturing and component requirements rather than relying on a generic stock-material callout.

Keep chemistry limits, specified mechanical minima, supplier informative data and approved design values separate. Retain traceability through forming, machining, joining and finishing. Release the finished component against its drawing, load and environmental requirements; neither a marine application list nor the words naval brass establish assembly qualification. The undated Concast sheet is identified by its explicit 2020 specification basis, not assigned a publication date from its crawl record.

## Related reference

[Grades, tempers and conditions](../grades-tempers-and-conditions.md)