New lumber treatment rapidly corrodes fasteners

By Alan J. Heavens
Knight Ridder Newspapers
March 13, 2004
Residential use of lumber treated with chromated copper arsenate (CCA)
has been banned for health reasons.
The pressure-treated-lumber industry has been developing alternatives,
including alkaline copper quaternary (ACQ). While not linked to any
health concerns, use of ACQ on lumber leads to a different problem:
The problem is not with ACQ itself, but with the fact that it is more
corrosive to screws and other fasteners used in building decks.
The building industry has discovered that contractors have been using
electroplated screws and fasteners in deck construction, just as they
did with CCA-treated lumber and with cedar and redwood.
However, the ACQ is quickly corroding those fasteners. The industry
recommends using the more expensive stainless steel or hot-dipped
galvanized fasteners instead. The hot-dipped fasteners, too, are subject
to corrosion -- just not as quickly as the electroplated screws.
Stanley Bostitch has come up with Thickcoat, a galvanized fastener that
has 21/2 times more zinc than electroplated screws. Chromate and polymer
coatings are then added for extra strength.
The technology differs from the common method of hot-dip galvanization,
which involves dipping a fastener in molten zinc, resulting in a porous,
non-uniform zinc coating.
Information: (800) 556-6696 or www.bostitch.com.

http://www.indystar.com/articles/4/128799-3244-053.html
Deborah Elaine Barrie
4 Catherine Street
Smiths Falls, On
Canada
K7A 3Z8
(613)284-8259

http://www.noccawood.ca
subscribe to list service at website