Lead: Characteristics, Uses and Problems

Procedure code:
501014G
Division:
Metals
Section:
Metal Materials
Last Modified:
08/10/2016

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Prior to inclusion in GSA’s library of procedures, documents are reviewed by one or more qualified preservation specialists for general consistency with the Secretary of Interior Standards for rehabilitating historic buildings as understood at the time the procedure is added to the library. All specifications require project-specific editing and professional judgement regarding the applicability of a procedure to a particular building, project or location. References to products and suppliers are to serve as a general guideline and do not constitute a federal endorsement or determination that a product or method is the best or most current alternative, remains available, or is compliant with current environmental regulations and safety standards. The library of procedures is intended to serve as a resource, not a substitute, for specification development by a qualified preservation professional.

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We’ve reviewed these procedures for general consistency with federal standards for rehabilitating historic buildings and provide them only as a reference. Specifications should only be applied under the guidance of a qualified preservation professional who can assess the applicability of a procedure to a particular building, project or location. References to products and suppliers serve as general guidelines and do not constitute a federal endorsement nor a determination that a product or method is the best alternative or compliant with current environmental regulations and safety standards.


References

  • Gayle, Margot, Look, David, and Waite, John. Metals in America's Historic Buildings: Uses and Preservation Treatments. Washington, DC: National Park Service, 1992.

  • Zahner, L. William. Architectural Metal Surfaces. New York: Wiley 2004.

Introduction

Characteristics of Lead

  • Very soft: without support, it can sag and become distorted.

  • Dense.

  • Durable.

  • Malleable.

  • Has a low melting point.

  • Long life-span (in milder climates, lead roofs have been known to last 200-300 years).

  • Generally corrosion-resistant - has little to no reaction with most compounds and solutions.

  • Resistant to corrosion by most acids including chromic, sulfuric, sulfurous and phosphoric acids.

  • Corrosive to alkalis (such as lime mortar, portland cement and uncured concrete), tannic acid found in wood, and radiation. Also corrosive to hydrochloric, hydrofluoric, acetic, formic and nitric acids.

NOTE: Ingestion of lead dust, typically through contact with older walls painted with lead paint, can result in serious long-term health problems, especially in the cases of young children or repeated exposure. See "Reducing Lead-Based Paint Hazards Using a Combination of Abatement and Interim Control Techniques on Windows" for more information and precautions associated with lead-based paint.

Typical Uses

Typical historical uses for lead included:
  • Lead Pipes: Sheets of lead were formed into tubes by bending and lead burning (welding).

  • Flashing, Gutters, Downspouts, and Conductor Heads: In roofing applications, lead was best used for flat or low pitch roofs and built-in gutters due to the heavy weight of the lead sheets.

  • Prior to the late 17th century, lead was cast by hand in sand beds. Later, lead sheets were rolled in the mill and were, consequently, much lighter. Lead-coated copper was introduced in the 1930s. This consisted of sheet copper dipped first in a lead-tin alloy, then dipped in pure lead and then rolled.

  • Lead-based paint.

  • Red lead was typically used as a corrosion inhibitor for use on iron.

  • White lead was used more frequently in commercial applications (white lead was not intended for use on iron - its use would increase corrosion, especially on wrought iron).

Typical current uses for lead include:
  • Sheet roofing.

  • Decorative spandrels.

  • Gutters, leader heads and downspouts.

  • Cast decorative features and sculpture.

  • Cupolas, spires and mullions.

  • Sheathing for cables.

  • Sheet lead partitions (good for noise reduction).

  • Pads for vibrating machinery.

  • Shielding for x-ray and nuclear radiation.

  • To waterproof ironwork where the iron is fitted into stone.

Natural or Inherent Problems

Chemical Corrosion

  • Lead has good corrosion resistance to the following acids: Chromic acid, sulfuric acid, sulfurous acid, and phosphoric acid.

  • Lead has poor corrosion resistance to: Alkalis like mortar and cement (evident as a reddish-brown oxide), carbon dioxide and organic acids like those found in wood (evident as a whitish carbonate coating).

  • Lead also has poor corrosion resistance to the following acids: Hydrochloric acid, hydrofluoric acid, acetic (i.e. fumes from breweries), formic acid (i.e. from ants and other insects), and nitric acid.

  • Lead is also susceptible to corrosion from tannic acid produced by oak, and acids from lichen on a roof that are washed over lead features such as flashing.

Galvanic (Electrochemical) Corrosion

  • Usually not a problem; lead is usually protected by a coating that forms on the surface and insulates the metal.

Mechanical or Physical Deterioration

  • Erosion and Abrasion: From dirt, sleet, hail and rain due to softness of metal.

  • Fatigue: Caused by thermal expansion and contraction

  • Buckling/Fatigue Cracking: May result from a high coefficient of thermal expansion.

  • Creep: Caused by the slow flow of gravity (usually a problem on steeper roofs). Creep and fatigue are often found together. One may accelerate the other.

Last Reviewed: 2017-08-13