Photo: BRANZ: Marine Environment Accelerates
Corrosion. (le) Bolt/Nut - 3 Years Mild
Environment;
(right) Bolt/Nut - 3 Years Marine Environment
By now, most
inspectors will have seen instances where a
relatively new deck or foundation has hardware that
inexplicably exhibits high levels of corrosion. In
some cases, it may be so significant that it le you
scratching your head wondering why? Beginning
in 2002, the chemical formulas used for
preservatively treated (PT) lumber were altered to
include much higher levels of copper. An
unintended consequence of this has been a
significant increase in metal corrosion where it
contacts the high-copper level PT materials. In
extreme cases, corrosion can be so severe that metal
connectors and fasteners may degrade to structural
failure in as little as six months. We have all seen
copper pipes directly connected to galvanized water
pipes. The galvanized pipes corrode because of the
reaction between the two metals. This is
EXACTLY
the same issue, except the copper is in the PT wood
and the ferrous metals that corrode are the nails,
screws, bolts, washers, nuts and structural metal
connectors.