Summary for aluminum with pressure treated lumber Discussion
Use of aluminum with pressure treated lumber is a corrosion concern, especially with newer copper-based treatments and in saltwater exposure. Franklin S. Beveridge asked whether hard-coat 6061-T6 aluminum angle would be protected from the copper in treated wood and whether any finish could prevent corrosion on a dock. Grady Knight replied that copper/aluminum corrosion has become widespread and said his team used either a wax coating with corrosion inhibitors or an acrylic aerosol spray with corrosion inhibitors; he noted both worked well in saltwater, with the wax coating offering better UV protection. A later commenter, Cathy Binkley, worried about a porch built with pressure-treated wood, aluminum flashing, and possibly regular nails. Linda Julius gave the strongest warning, saying aluminum and pressure treated wood do not mix and that aluminum in contact with the wood will eventually pit and develop holes. The thread overall advises caution and protective coatings, but not a guaranteed fix.
I would like to know if I hard coat 6061-T6 Aluminum angle will it protect it from the copper used in the pressure treatment. If not is there any finish I could apply to the angle to keep it from corroding. The use is in a salt water environment (dock) not immersed in the water.
Thank you very much for your time.
Franklin S. Beveridge
Briarpatch Engineering – Pocasset, Massachusetts
2006
There is an epidemic nationwide of copper/aluminum corrosion since wood treatments changed to high copper for environmental reasons. I worked with our state department of transportation to solve the problem on the highway signs. We used one of two different materials one a wax coating with corrosion inhibitors. The other was an acrylic aerosol spray again with corrosion inhibitors. Both coatings work well in saltwater environments. The wax coating provides better UV protection.
Regards,
Grady Knight
– Colville, Washington, USA
2006
I recently had a porch re-built and the contractor used 2 by 6 inch pressure treated wood to build the support beam. He covered it with aluminum flashing and may have used regular nails to attach the roof beams and ceiling joints to the beam.
Should I be concerned that the nails will corrode in a year and the aluminum flashing will corrode as well? All the info I have found indicates that my porch could fall down in a few years due to corrosion. CB
Cathy Binkley
– Louisville, Kentucky, USA
2007
A. You should be very cautious. Aluminum and pressure treated wood do not mix. Where aluminum comes in contact with the wood, the aluminum will eventually pit and holes will appear.
Linda Julius
– Louisville Kentucky
October 10, 2013