5-6 years ago the pressure treated lumber that we used everyday for picnic tables, decks, swingsets, facia boards, etc. was switched to a different formula in which the preservative lumber was treated with. Arsenic was the main ingredient used and replaced with a chromium and quam mixture to make it safer for children and adults in contact with it. The only problem was the new chromium, quam mixture was highly acidic to all electrogalvanized nails and aluminum products it came in contact with. In result of these findings, installers had to switch to hot dipped galvanized nails and use copper flashing before use of aluminum to prevent corrosion. As of a few months ago, lumber companies have produced a different mixture allowing a safe and effective way to treat lumber again that is not acidic to aluminum and electrogalanized products. This is new on the market and installers must know the difference in between the two pressure treated mixtures on the market to avoid complete failure in a project.