OT63 Brass

OT 63 brass (CW508L, also known as 63/37 brass) is one of the most popular alloys in industry, thanks to its perfect balance of copper (63 percent) and zinc (37 percent). Characterized by NSF/ANSI 372 certification-which certifies its compliance with the requirements for materials in contact with potable water-this brass belongs to the lead-free alloys, meeting the current Ministry of Health regulations for water systems. The peculiarity of the semi-hard state gives the sheet such ductility as to allow bends up to 90° and beyond, without triggering cracks or breaks. This opens up endless possibilities for mechanical processing (from laser cutting to blanking, water cutting to traditional milling) and surface treatments (satinizing, polishing, burnishing, chrome plating, painting).

Advantages of OT 63 brass

High cold workability: The semi-crude condition of the sheet allows deep plastic deformation without structural failure. 90° bends, deep drawing, coining and coil bending are extremely easy, reducing tooling and part acceptance times. This is particularly advantageous for mass production of parts with complex geometries, where high precision and repeatability are required.

Good corrosion resistance: Due to the significant percentage of copper and low affinity for aggressive atmospheric reagents, OT63 maintains excellent surface stability over time. It is widely used in marine settings, plumbing fixtures, faucets and heat exchangers, where the combined action of water, moisture and thermal changes could compromise the durability of less noble materials.

Remarkable thermal and electrical conductivity: 63/37 brass has a thermal conductivity of about 110-120 W/m-K and an electrical conductivity of about 28 percent IACS, values that make it suitable for components for electrotechnical applications, such as electrical contacts, connectors, ground plates, and EMI/RFI shields. In addition, good thermal transmission makes it suitable for heat exchanger parts and industrial radiators.

Food and Sanitary Compatibility: Compliant with NSF/ANSI 372 and lead-free (or less than 0.25 percent content), OT 63 is widely used in faucets, valves, fittings for drinking water systems and in the food industry, where direct contact with liquids intended for consumption requires non-toxic and stable materials over time.

Economic balance: Compared to other brass alloys with higher copper contents (such as the more expensive OT 67), OT 63 offers a lower cost per kilogram while still providing a high level of mechanical and chemical performance. This makes it a preferred solution for many industrial applications where cost/performance is a determining factor.

Adaptability to surface treatments: The microstructure of OT 63 readily accepts both matte (satin-finishing, burnishing) and glossy (mirror polishing, electropolishing) aesthetic finishes, as well as painting and chrome plating. This makes it possible to obtain components that are both functional and pleasing in architectural and design contexts.

Limitations and critical issues

Less smooth hot processing: While OT 63 is excellent when cold, it does not achieve the same chip removal fluency as leaded alloys (e.g., OT 58). During turning and milling, it is necessary to optimize cutting parameters, use high-quality coolant lubricants, and tools with suitable coatings to avoid material adhesion and continuous chip formation that compromise surface finish.

Lead-free: The elimination of lead, while beneficial from an environmental and health standpoint, reduces the "softness" of the alloy in machining operations. This results in faster tool wear and the need for frequent tool changes or post-machining heat treatments to restore surface ductility.

Moderate mechanical strength: With typical tensile strength values between 350 and 400 MPa and a yield strength around 100-150 MPa, OT 63 is suitable for multiple uses, but it does not compete with high-performance structural wedges (for which special steels or alloys with tin, iron or lead additives are preferred). In applications subject to high dynamic loads or intense vibration, safety margins must be carefully considered.

Difficult to weld with traditional methods: Although weldable by specific techniques (GTAW with silicon or phosphor filler wire), OT 63 brass requires experienced operators and careful controls to avoid internal porosity or heating cracks. Gas (oxyacetylene) welding must be performed with dedicated protective fluxes to prevent oxide inclusions.

High specific gravity: With a density of about 8.4 g/cm³, OT 63 is significantly heavier than aluminum or magnesium. In projects where weight affects energy consumption (aerospace, automotive, transportation), it is necessary to balance its excellent mechanical properties with possible structural limitations.

Typical sheet metal applications

OT 63 brass in sheet metal format finds use in multiple areas due to its aesthetic and functional versatility. In the metalwork and furniture industry it is used to make decorative panels, paneling and partitions requiring elegant perforated patterns, as well as ventilated facade cladding. Finishing profiles such as cornices, skirting boards and flat handles benefit from the natural luster and dimensional stability of this alloy, while designer lamps, trays and shelves take advantage of its machinability to achieve harmonious shapes and refined details.
In construction, OT 63 is used for cover plates on armored doors and locks, as well as for finishing elements on pushbuttons and intercoms, where corrosion resistance ensures durability even in outdoor environments. Similarly, the electrotechnical industry takes advantage of the electrical conductivity qualities of 63/37 brass for contacts and terminals, ground plates and EMI/RFI shields, ensuring protection and reliability in the most sensitive applications.
The use of OT 63 also extends to the world of art and advertising: signs, shaped letters and customized plaques are precisely shaped, offering a warm color contrast and a polished or satin finish as required. In the field of sacred art, sheet brass is chosen for crosses, friezes and reliquaries that require a combination of light weight and corrosion resistance.
In light metalwork, spacers, brackets and reinforcing plates take advantage of the material's ductility and conductivity, while gaskets and insulating supports benefit from its excellent dimensional stability. Also in musical instrument construction, OT 63 is valued for reinforcing plates and secondary protectors of wind instruments, as well as for aesthetic details in finishing parts.
Finally, laser cutting on OT 63 brass sheet allows for complex geometries and very tight tolerances without the need for additional finishing. This technology is now of reference in industrial design applications, interior and exterior furnishings, artistic signage, custom automotive and motorcycle components, as well as in the manufacture of small metal parts for jewelry and high-end fashion.

Comparison with other materials

Brass OT 58 (CuZn40Pb2): OT 58, enriched with lead (up to 2 percent), excels in ease of machining, offering broken chips and less tool wear. However, it exhibits lower cold deformability and does not always comply with standards for potable use. OT 63, while requiring more accurate cutting parameters, provides superior performance in food and sanitary applications.

Brass OT 67 (CuZn33): With a higher copper content, OT 67 offers slightly better corrosion resistance and higher toughness; however, the raw material cost is considerably higher and cold workability may be less readily available than OT 63.

Leaded brass: Alloys with high lead content (up to 3 percent) are among the "softest" for milling and blanking, but do not meet environmental and health requirements for water use. OT 63 thus represents a meeting point between material healthfulness and processing quality.

Aluminum5754 (Al-Mg): Aluminum 5754, with a density of about 2.67 g/cm³, is more than three times lighter and has superior corrosion resistance in marine environments due to its protective oxide layer. However, from the standpoint of electrical conductivity (only about 30 percent IACS of brass) and thermal conductivity (130-150 W/m-K of aluminum versus 110-120 W/m-K of OT 63), brass remains a material of choice for heat exchangers and electrical components. Aluminum excels in TIG/MIG weldability and cold formability, but struggles to offer fine aesthetic finishes without more complex subsequent treatments.

Stainless steels(300 series): Stainless steels provide superior mechanical strengths and excellent corrosion resistance, but thermal and electrical conductivity is lower and cold workability requires more powerful forces and tooling. OT 63 brass remains preferred where good conductive properties and a low-cost polished or satin finish are needed.

Conclusion

OT 63 brass proves to be an extremely versatile and balanced alloy, ideal for a wide range of mechanical, architectural, electronic and design applications. The semi-hard state allows fast and reliable productions, with complex bending and forming without risk of cracking. NSF/ANSI 372 certification and lead-free status make it safe for use in contact with drinking water and food. Although it presents some challenges in hot processing and lower mechanical strength than special alloys or stainless steels, its competitive price, thermal and electrical conductivity, and refined aesthetics make OT 63 the benchmark solution when looking for a ductile, corrosion-resistant and easy-to-finish material. When choosing between OT 63 and alternative materials (OT 58, OT 67, aluminum 5754, stainless steels), the designer will need to evaluate factors such as operating environment, mechanical requirements, conductivity, weight, and health regulations in an integrated manner to identify the alloy or metal that optimizes cost and performance of the final product.