Lead Content
To enhance the machinability of brass, lead is often added in concentrations of around 2%. Since lead has a lower melting point than the other constituents of the brass, it tends to migrate towards the grain boundaries in the form of globules as it cools from casting. The pattern the globules form on the surface of the brass increases the available lead surface area which in turn affects the degree of leaching. In addition, cutting operations can smear the lead globules over the surface. These effects can lead to significant lead leaching from brasses of comparatively low lead content.
Silicon is an alternative to lead; however, when silicon is used in a brass alloy, the scrap must never be mixed with leaded brass scrap because of contamination and safety problems.
In October 1999 the California State Attorney General sued 13 key manufacturers and distributors over lead content. In laboratory tests, state researchers found the average brass key, new or old, exceeded the California Proposition 65 limits by an average factor of 19, assuming handling twice a day. In April 2001 manufacturers agreed to reduce lead content to 1.5%, or face a requirement to warn consumers about lead content. Keys plated with other metals are not affected by the settlement, and may continue to use brass alloys with higher percentage of lead content.
Also in California, lead-free materials must be used for "each component that comes into contact with the wetted surface of pipes and pipe fittings, plumbing fittings and fixtures." On January 1, 2010, the maximum amount of lead in "lead-free brass" in California was reduced from 4% to 0.25% lead. The common practice of using pipes for electrical grounding is discouraged, as it accelerates lead corrosion.
Read more about this topic: Brass
Famous quotes containing the words lead and/or content:
“Politics at all times lead to bloody wars, and not only politics, but also religions as well as social and economic systems of all times are spattered with blood. Invariably the big ones devoured the little ones, and the little ones the tiny ones.”
—Friedrich Dürrenmatt (1921–1990)
“A person of mature years and ripe development, who is expecting nothing from literature but the corroboration and renewal of past ideas, may find satisfaction in a lucidity so complete as to occasion no imaginative excitement, but young and ambitious students are not content with it. They seek the excitement because they are capable of the growth that it accompanies.”
—Charles Horton Cooley (1864–1929)