Material Choice: GLOSSARY

This glossary accompanies the exhibit Material Choice: Science, Conservation, and Public Art and is for visitors interested in further definitions of scientific, conservation, and public art terms.

accelerated corrosion tests - methods designed to approximate, in a short time, the deteriorating effect under normal long-term service conditions.

adhesive- a material or quality that allows some substance to hold two or more materials to together. Distinguished from cohesion.

alloy- a metal made by combining together two or more metals together. For examples, brass is an alloy of copper and zinc, bronze is an alloy of copper and tin, and steel is an alloy of iron and carbon.

anode- the electrode of an electrolytic cell at which oxidation or corrosion of some component occurs (opposite of cathode). Electrons flow away from the anode in the external circuit.

anodic corrosion- the dissolution of a metal acting as an anode.

artist, public- an artist who makes art for public spaces.

art conservator, public- trained in the areas of fine art, history, and science, a conservator’s main goal is to preserve cultural property for the future, supported by research and education. In contemporary public art, the conservator assists both the public artist and the arts agency and works in collaboration with urban design professionals and arts fabricators.

arts agency- an organization that advocates for the arts and administers arts programming.

austenitic stainless steels- types of steels containing high percentages of certain alloying elements such as manganese and nickel which are austenitic (having FCC face centered cubic crystal structure) at room temperature They are non-magnetic. Examples of austenitic steels include the 300 series (such as Type 304 and Type 316).

bronze, statuary- sometimes referred to as “historic” bronze. An alloy of copper and tin sometimes containing small amounts of zinc or lead used to cast bronze sculpture. A typical US standard statuary bronze would be approximately 90% copper, 7% tin and 3% zinc.

bronze, silicon- commonly used in contemporary art foundries. Silicon bronzes vary in composition from 91-98% copper, 0.5-3.5% silicon, 0-6% aluminum, 0-25 nickel, 0-1.5% zinc, and 0-2% tin. Silicon bronze has greater resistance than statuary bronze to wear and corrosion, even in marine environments.

cathode- the electrode of an electrolytic cell at which reduction is the principal reaction (opposite of anode). Electrons flow toward the cathode in the external circuit.

chloride salts- naturally occurring soluble salts found in marine environments that cause a certain type of corrosion to metals, often occurring quickly. Chloride salts are also present in road salt, used to melt ice during snow removal.

cohesive- the force by which molecules of a substance are held together. Differentiated from adhesion.

corrosion- the chemical or electrochemical reaction between a material, usually a metal, and its environment that produces a deterioration of the material and its properties.

electrolytic cel- an electrochemical system consisting of an anode and a cathode in metallic contact and immersed in an electrolyte. (The anode and cathode may be different metals or dissimilar areas on the same metal surface).

electroplating- electrodepositing a continuous metal or alloy in an adherent form on an object serving as a cathode.

environment- the surroundings or conditions (physical, chemical, mechanical) in which a material exists.

fluoropolymer- a compound containing atoms of fluorine bound to the polymer molecule, and is characterized by an unusually high resistance to solvents, acids, and bases.

galvanic corrosion or dissimilar metal corrosion- an accelerated corrosion of a metal due to electrical contact with a more noble metal or nonmetallic conductor in a corrosive electrolyte. Galvanic corrosion will occur when two metals of different electrochemical potential come in contact with each other in the presence of water or high humidity.

galvanic series or electropotential series- a list of metals and alloys arranged according to their relative corrosion potentials in a given environment. When two metals are submerged in an electrolyte, while electrically connected, the less noble will experience galvanic corrosion. The rate of corrosion is determined by the electrolyte and the difference in nobility.

high-performance coating - in modern paint technology, a surface coating of paint that offers outstanding adhesion, ultra-violet light resistance, and abrasion resistance, often used in industrial applications.

maintenance- in public art, the act of routinely caring for a publicly sited artwork or installation.

monomer- a molecule, usually an organic compound, having the ability to join with a number of identical molecules to form a polymer.

patina, applied- chemicals and pigments intentionally used to synthetically induce a thin, uniform, usually aesthetic or decorative surface on metal patina on a metal surface, particularly bronze. Without a protective coating, an applied patina on an outdoor bronze is not stable, and will alter over time.

---hot patina- many patination techniques use heat to chemically form mineral products with variations in color and tone on the surface of bronze.

---cold patina- a patination technique using chemicals at room temperature to form mineral products in variations of color and tone on the surface of bronze. The patina products formed may not adhere as well as those formed by hot patina.

---foundry patinators- are experts in applied patinas, understanding the differences between alloys, heats, and chemical reagents to achieve a certain color and effect. Some patinators will develop a certain patina specifically for one sculptor.

periodic table- an arrangement of the chemical elements ordered by increasing atomic number in columns (groups) and rows (periods) presented so as to emphasize their physical characteristics and chemical behavior. The periodic "law" of chemistry recognizes that many properties of the elements are periodic functions of their atomic number (the number of protons within the element's atomic nucleus).

polymer- a high molecular weight compound formed by the combination of one or more monomers. Rubber granules SBR and EPDM are polymers.

powder coating- a thermosetting resin preparation used to evenly coat metallic pieces without the use of solvents. Powder coatings were introduced about 1960 but only became popular when solvents were tightly restricted at the end of the twentieth century. Electrodeposition is used to uniformly coat a metal object with the finely ground resin, then heat is used to fuse the particles into a hard, resistant film.

pre-fabrication review- in public art conservation, a detailed review of materials and techniques to be used for an artwork or installation, involving the artist, architect, fabricator, commissioning agency, landscape architect, engineer, and other collaborators. Specific products and techniques are discussed and chosen, and the artist and collaborators agree on a maintenance plan.

protective coating- in bronze conservation, a replenishable, reversible surface coating used to protect the metal from the environment, particularly from acid deposition. They may also be used as a sacrificial coating for graffiti removal. Typical coatings include hard paste waxes or a combination of a lacquer and hard paste wax, and usually must be maintained annually.

stainless steel- an iron alloy with at least 10.5% chromium content. Chromium gives steel hardness and corrosion resistance. The addition of nickel to the alloy strengthens the surface layer and makes the steel austenitic. The addition of molybdenum protects the metal from corrosion caused by chloride salts.

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