Galvanic action, the electro-chemical process that causes corrosion in certain materials when in contact with dissimilar materials, can cause certain metals to lose strength and eventually fail. One such interaction is when aluminum is in contact with pressure treated wood. The pressure treated wood contains copper, along with other metals, that interacts with aluminum and causes the corrosion. By following a few simple steps, the dissimilar materials can be separated and the corrosion process stopped.
Determine the points of contact between the treated wood and the aluminum. Often, it is the fasteners or connectors that creates the contact point.
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Use plastic or polymer washers to separate the materials from the fasteners, if it is determined that it is the fasteners that are creating the contact points. These rubber-like washers, which are available at many home improvement stores, insulate the two materials against making contact.
If the contact points occur along the entire length of a treated wood member, you should remove that piece of structure and install a non-treated wood member instead. This will prevent galvanic action and eliminate the risk of corrosion. Alternately, a rubber or plastic mat or sheet can be installed between the treated wood and aluminum to eliminate contact points.