Pressure-treated wood is truly a rugged exterior building product that is rot and insect resistant. Treated wood is used for a number of exterior building applications. Pressure treatment is a process that forces chemical preservatives into the wood. Wood is placed inside a closed cylinder, and vacuum and pressure are applied to force the preservatives into the wood. The preservatives help protect the wood from attack by termites, other insects, and fungal decay.
Hot-dip galvanized or stainless steel fasteners, anchors and hardware are recommended by the Pressure Treated Wood Industry for use with treated wood. This prevents the fasteners from decaying faster than the wood itself. In the past this industry did not address the required levels of galvanizing, however most of those in the industry now provide information regarding the minimum level of galvanizing that should be used.
In general, the thicker the galvanized coating the longer the expected service life of the fastener, connector, anchor, or other hardware will be. Mechanical galvanizing is a process of providing a protective coating (zinc) over bare steel. The bare steel is cleaned and loaded into a tumbler containing non-metallic impact beads and zinc powder. As the tumbler is spun, the zinc powder mechanically adheres to the parts. The zinc coating has “good” durability, but has less abrasion resistance than hot-dip galvanized zinc coatings since it does not metalurgically bond with the steel. Some anchors and fasteners can be mechanically galvanized.
An alternative to mechanical galvanizing is hot-dip galvanizing Hot-dip galvanizing is the process of coating iron or steel with a thin zinc layer, by passing the steel through a molten bath of zinc at a temperature of around 460° C. In general, a heavier/thicker coating would be expected to have a longer service life than standard galvanized connectors.
Typically, pin and washer combinations are used as fastener systems in powder actuated fastening devices. Commonly known as Powder Actuated Tools, these devices force a pin through a washer into the wood with sufficient force to embed the pin in a single stroke. Typically, a fastener is initially coupled to a metallic washer with a through-hole having a diameter smaller than the diameter of a fastener. This ensures that the pin and washer stay in place when loaded in to the fastening device, and are secure when the device is forced downward (toward the wood), typically to deactivate a safety device present in the tool which prevents accidental firing of the fastener. When used with standard applications of washers having a through-hole with a diameter smaller than the diameter of a fastener, the washer can scratch off a galvanized coating, eliminating or reducing the benefits of the zinc layer.