Copper, Brass, and Bronze Surfaces

A Guide to Alloys, Finishes, Fabrication, and Maintenance in Architecture and Art

L. William Zahner

• Publisher: Wiley
• Year: 2020
• ISBN:
  9781119541684
• Edition: 1
• Topic: Architecture
• Subtopic: Architecture Methods & Materials

A FULL-COLOR GUIDE FOR ARCHITECTS AND DESIGN PROFESSIONALS TO THE SELECTION AND APPLICATION OF COPPER, BRASS, AND BRONZE

Copper, Brass, and Bronze Surfaces, third in Zahner's Architectural Metals Series, provides a comprehensive and authoritative treatment of copper, brass, and bronze applications in architecture and art. If offers architecture and design professionals the information they need to ensure proper maintenance and fabrication techniques through detailed information and full-color images. It covers everything from the history of the metals and choosing the right alloy, to detailed information on a variety of surface and chemical finishes and corrosion resistance. The book also features case studies that offer strategies for designing and executing successful projects using copper, brass, and bronze.

Copper, Brass, and Bronze Surfaces is filled with illustrated case studies that present comprehensive coverage of how each metal is used in creating surfaces for building exteriors, interiors, and art finishes. All the books in Zahner's Architectural Metals Series offer in-depth coverage of today's most commonly used metals in architecture and art. This visual guide:

• Features full-color images of a variety of copper, brass, and bronze finishes, colors, textures, and forms
• Includes case studies with performance data that feature strategies on how to design and execute successful projects using copper, brass, and bronze
• Offers methods to address corrosion, before and after it occurs
• Explains the significance of the different alloys and the forms available to the designer
• Discusses what to expect when using copper, brass, and bronze in various exposures

Written for architecture professionals, metal fabricators and developers, architecture students, designers, and artists working with metals, Copper, Brass, and Bronze Surfaces offers a logical framework for the selection and application of copper, brass, and bronze in all aspects of architecture.

CHAPTER 1
Introduction—Element 29

Copper and Copper Alloys

Cu—Cuprum

INTRODUCTION

Of the metals, only copper and gold possess colors other than gray or silver in their natural forms. When copper is combined with different elements, elegant colors and tones can be produced both naturally and artificially. This is the reason why our ancient ancestors first worked with this metal: they could identify it among rocks and stones more easily and it was more abundant than gold. The brightly colored ores of copper, malachite, and azurite surely attracted the attention of early humans. These were not your normal rocks.

Copper is element 29 in the periodic table (Figure 1.1). It falls between element 28 (nickel) and element 30 (zinc). Copper is in the same group as silver and gold: metals that it mixes with and that possess similar properties of electrical and thermal conductivity. Like copper, gold and silver were also highly valued by early man. Being more abundant, copper took on the heaviest workload. The age named for it marks an advance in civilization.

Copper possesses a face‐centered cubic structure in its pure state, but this structure changes as alloying elements are added (Figure 1.2). This face‐centered structure is shared with many other metals, such as aluminum and iron.

The atomic makeup of copper is responsible for many of the unique attributes this metal offers (Figure 1.3). The atomic number of 29 means that copper has 29 protons in the nucleus with 29 electrons making up its outer shells. It is the lone electron in its fourth orbital that gives copper one of its most important traits. This electron is free to move about, allowing electrical current to move easily from atom to atom.

FIGURE 1.1 Copper's position in the periodic table of elements.

FIGURE 1.2 Face‐centered cubic structure of a copper crystal.

FIGURE 1.3 Copper atom.

This lower resistance coming from a single electron in the outer orbit gives copper its exceptional ability to transport electricity. The metals whose atoms have the fewest electrons in their outer (or valence) shell offer the least resistance to the movement of electricity from one atom to the next. Gold, silver, and copper are metals that have only one electron in their valence shells, which gives them their ability to conduct electrical current more efficiently than atoms with more than one electron. This lone electron moves freely around and through the lattice structure of the metal, transferring the electrical current with little resistance. Aluminum has three electrons in its valence orbit, while zinc, nickel, iron, and titanium have two (Table 1.1).

Operating under a principle similar to electrical conductivity, the conductivity of heat has the same order across metals. Alloying will change the heat conductivity of a particular metal, as it does the electrical conductivity. For instance, most bronze alloys of copper will not conduct as well as many aluminum alloys. The alloying elements in bronze diminish its ability to move an electrical charge.

As they are essentially shared, these valence electrons are free to flow in and around the atoms, creating a “sea” of charged particles. This sea of electrons allows the charge to move rapidly and with little resistance as energy is transferred from electron to electron that collectively make up the sea around the copper atoms (Figure 1.4).

Most of the copper found on the Earth's surface is from hydrothermal activity that brought the metal to or near the surface. Other surface copper is drift copper, deposited by glacier activity and randomly set in rubble. Copper makes up approximately 0.0068% of the upper mineral crust of the Earth and is widely distributed with concentrations in select regions.

Copper has a poor strength‐to‐weight ratio as compared to other metals used in industry. However, copper alloys, such as brass alloys, have a strength‐to‐weight ratio equivalent to stainless steels.

TABLE 1.1 Electrical conductivity of various metals in siemens m⁻¹ at 20 °C.

Metal	Siemens m^−1
Silver	6.30 × 10^7
Copper	5.98 × 10^7
Gold	4.52 × 10^7
Aluminum	3.50 × 10^7
Zinc	1.68 × 10^7
Nickel	1.43 × 10^7
Iron	1.04 × 10^7
Titanium	1.80 × 10^6

FIGURE 1.4 Sea of shared electrons around the metal atoms of copper.

Other characteristics of copper include excellent ductility, a deep forming ability, high fracture toughness, high elasticity (resiliency under shock loading), and soft edges.

Copper is also nontoxic—although copper salts are considered ecotoxic in certain instances—and has superior corrosion resistance in many natural environments.

Copper: Element 29

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