Lead: Characteristics, Uses And Problems
LEAD: CHARACTERISTICS, USES AND PROBLEMS
This standard includes general information on the characteristics
and common uses of lead and identifies typical problems associated
with this material along with common causes of its deterioration.
Margot Gayle, David W. Look, John Waite. Metals in America's Historic Buildings. Washington, DC: National Park Service, 1992.
L. William Zahner. Architectural Metals. New York: John Wiley & Sons, Inc., 1995.
Characteristics of Lead:
- Very soft: Without support, it can sag and become distorted
- 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.
Typical historical uses for lead included:
- Lead pipes: Sheets of lead were formed into tubes by bending
and lead burning (welding).
- Flashing, gutters and downspouts, and conductor heads
- 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. In roofing applications, lead was
best used for flat or low pitch roofs and built-in gutters due
to the heavy weight of the sheets. Lead-coated copper was
introduced in the 1930's. This consisted of sheet copper
dipped first in a lead-tin alloy, then dipped in pure lead and
- Lead-based paint (historical use): 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
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
1. Chemical Corrosion:
a. Lead has good corrosion resistance to the following
acids: Chromic acid, sulfuric acid, sulfurous acid, and
b. 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).
c. 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.
d. 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.
2. Galvanic (Electrochemical) Corrosion: Usually not a problem;
lead is usually protected by a coating that forms on the
surface and insulates the metal.
3. Lead as component of older paint coatings; health hazards: Ingestion of lead
dust for workers and young children can result in serious
lint-term health problems. See 09900-04-S for more
information and precautions associated with lead-based paint.
VANDALISM OR HUMAN-INDUCED PROBLEMS
Mechanical or physical deterioration:
1. Erosion and abrasion: From dirt, sleet, hail and rain due to
softness of metal.
2. Fatigue: Caused by thermal expansion and contraction
3. Buckling or fatigue cracking: May result from a high
coefficient of thermal expansion.
4. 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.
END OF SECTION