If this is the new "Copper Quaternary" pressure treated lumber, people
might want to know "WHY" it eats fasteners.
They used to treat pressure treated lumber with a mixture of copper and
arsenic salts dissolved in water.
The found that the arsenic was being leached out of pressure treated
lumber in contact with the ground and showing up in shallow wells people
used for their water supply. So, they banned arsenic in pressure
To get the same protection without arsenic, they had to quadruple the
amount of copper in the pressure treatment liquid they force into the
Since copper is more noble on the galvanic scale than either zinc or
iron, when this new copper quaternary pressure treated wood gets wet,
you end up with a lot more galvanic corrosion of zinc plated and
unplated iron fasteners than you did with the old arsenic bearing
pressure treated lumber.
So, now the recommendation is that people use triple galvanized or
stainless steel fasteners and hardware on the new pressure treated
lumber to allow for the much higher galvanic corrosion rates cuz of the
increased amount of copper.
To make this experiment meaningful, you need to make sure that your
pressure treated wood is in contact with the ground or a source of
moisture all the time since the corrosion process is primarily galvanic
corrosion. You won't get any galvanic corrosion in completely dry wood.