Why Iron Stains Wood...
Sunday, December 13th, 2009
Iron stain is that unsightly
blue–black or gray discoloration that can occur on
nearly all woods. Oak, redwood, cypress, and cedar
are particularly prone to iron stain because these
woods contain large amounts of tannin-like
extractives. The discoloration and subsequent
streaking is caused by a chemical reaction between
extractives and iron in steel products, such as
nails, screws, and other fasteners.
Coatings for fasteners, such as
galvanizing (zinc) or ceramic coatings, give a wide
range of performance. Shiny galvanized fasteners are
electroplated with zinc. The zinc coating is very
thin and fails quickly because it really is just a
sacrificial coating. Dull-gray galvanized fasteners
are mechanically coated and can last longer than
electroplated fasteners; however, because the zinc
coating has significant amounts of iron, staining is
likely. Hot-dipped (double-dipped) galvanized
fasteners, recognized by their "globby" appearance,
give the longest protection to the steel. The globs
of zinc on a hot-dipped galvanized screw can clog
the head, making the screw difficult to use.
Therefore, stainless steel is the best choice for
fasteners, particularly screws.
If you have any
questions or comments about this blog entry please
do not hesitate to
send me an e-mail. Thanks and be
safe when working with tools!!!
Robert Burgoyne, also known as "Burgie",
has been doing woodworking for nearly 30
years. He started learning at an early
age in his grandfather's garage and
continued while working with his father
in construction. The hobby has now
become a business with Creative
Landscape Accents. Burgie builds
high quality woodworking projects for
the outdoors and also enjoys making
decorative accent pieces for inside the
house. While not working in his shop
doing woodworking Burgie enjoys
computers, restoring his old
Chevy C60 2-ton dump truck and
riding his Harley-Davidson Road King
throughout beautiful Colorado.