Exhibit Area 1
(Plaza area)
Welcome Sign [main directory]
How the Bridge Spans the Golden Gate
Bridge Aesthetics - Art Deco on a Grand Scale
Tall and Strong - The Bridge Towers
Steel, Fog, Salt, Rust, and Paint

Exhibit Area 2
(near flagpole)
How the Bridge Vibrates
Foghorns

Exhibit Area 3
(West side of Bridge near underpass)
Historic Preservation: Lattice Strut Retrofit
Historic Preservation: Isolator Seismic Retrofit

Exhibit Area 4
(inside Battery area)
History: Design and Construction of the Bridge
Suspension Cable Tension vs. Tower Height
Battery Lancaster - Defending the Golden Gate

Exhibit Area 5
(along bike path to lower parking lot)
Bridge Deck Aerodynamics
Bridge Deck Torsional Resistance Retrofit
Wind Speed and Wind Pressure

Exhibit Area 6
(near Pavillion)
LIFETILES: animated construction of the Bridge
Braille / Tactile Model of the Bridge



Project Partners

GGBHTD
Golden Gate Bridge,
Highway and Transporation District



CUREE

Consortium of Universities for Research
in Earthquake Engineering

Main Menu : Exhibit Area 1

Steel, Fog, Salt, Rust, and Paint

Only rarely must the Golden Gate Bridge withstand earthquakes or strong wind, but everyday it must fight another threat: corrosion of the steel which creates a byproduct called rust.

Steel is an alloy comprised principally of iron along with small amounts of other elements such as carbon or nickel. When steel is exposed to the oxygen in air and to water, the iron changes through a chemical process called corrosion; this change creates rust which erodes the steel making it slightly smaller and weaker than before the corrosion took place. On the Bridge, fortunately, the steel sections were originally over-sized in anticipation of corrosion and other threats.

Water vapor evaporating from the ocean is all around the Bridge and often cools and condenses to form fog. Corrosion is sped up by the presence of salt. The sea air around the Bridge not only supplies the water needed for rust -- it is also loaded with millions of tiny particles of salt.

In the 1930s the original primer paint on the Bridge was two-thirds (by weight) lead. Lead is a good material for preventing rust, but is harmful to people and the environment. Today different areas of the Bridge are re-painted about every ten to twenty years. Due to environmental concerns, today’s primer contains zinc instead of lead. The zinc protects the steel, because zinc corrodes more easily than steel. Zinc serves as a sacrificial metal, so the steel does not rust when zinc is present. On top of that zinc primer is a top coat of paint in the Golden Gate Bridge’s signature color called International Orange.

More Images

Close-up of Rivets with Rust -
When the protective paint layer peels or cracks, steel is exposed to oxygen and water which initiates corrosion. Maintenance is required to remove the rust down to bare steel before re-applying primer and top coats of paint.

Besides International Orange, other color schemes were considered when the Bridge was built. One alternative that was proposed was a striped design to make it more visible to ships and airplanes.

Fog in the Golden Gate.

More fog in the Golden Gate.


All images property of the Golden Gate Bridge, Highway and Transportation District (unless otherwise indicated).

For more information -

http://goldengatebridge.org/research/factsGGBIntOrngPaint.php


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Last updated: 11.13.12