"The many variables present in a single building environment make it impossible to accurately predict if, or when, significant corrosion will begin or reach a critical level. This relative uncertainty makes it crucial that the specifiers be knowledgeable of the potential risks and select a product coating or metal that is suitable for the intended use." "Changes in the preservative-treated wood industry have created additional concerns. Effective Dedecemvber 31, 2003, the preservative-treated wood industry voluntarily changed from Chromated Copper Arsenate (CCA-C) used in residential applications to alternative treatments. Testing has shown that certain alternative replacement treatments are generally more corrosive than CCA-C." "Historically, the connector (hanger & support) industry has used products manufactured with a G60 coating, which means .60 ounces of zinc per square foot total for both sides of the sheet steel combined. In recent years, Simpson made the decision to increase the minimum standard amount of zinc protection to a G90 coating, .90 oz./square foot total for both sides of the metal combined. Simpson also offers many products with ZMAX, which is a G185 coating, 1.85 oz./square foot total for both sides of the metal combined." Keep in mind, the G185 Specification refers to the plating on 'sheets' of metal. So when we speak of 1.85 ounces of zinc per square foot, this refers to the amount of zinc on both sides of the sheet metal combined!. This was actually increased from the previous G90 Specification of .90 ounces of zinc on both sides of the sheet metal combined! Although these are similar specifications, the G185 Coating Designation covered under the ASTM A653 Specification, referring to the plating of sheets of steel, and ASTM A153 referring to the plating of bolts, these really can't be compared. But given the recent recommendations in the building industry, if we really need to compare these two specicications, the 1.25 ounces of zinc plating covering the bolt per the ASTM A153 Specification, is actually heavier than the 1.85 ounces present on both sides of the sheet metal combined per the G185 Coating Designation (i.e. 1.85 x .5 = .93 ounces of zinc per square foot per side.) "Due to the uncertainties, which are out of the specifier's control, in regard to the chemicals used in pressure treated wood, Simpson recommends the use of stainless steel fasteners, anchors and connectors with treated wood when possible." "At a minimum, customers should use ZMAX (G185 Hot Dip Galvanized per ASTM A653), Batch/Post Hot Dip Galvanized per ASTM A123 for connectors and ASTM A153 for fasteners, or mechanically galvanized fasteners per ASTM B695, Class 55 or greater." "Due to the many variables involved, many of which are controlled by the chemical supplier and the wood treater, Simpson cannot make an unqualified recommendation of any galvanized or other coating for use with treated wood." "Additionally, because of the many variables involved," Simpson states, "we cannot provide estimates on service life of connectors, anchors, or fasteners. We suggest that all users and specifiers obtain recommendations for Batch/Post Hot Dip Galvanized, G185 Hot Dip Galvanized, mechanically galvanized, or other coatings from their treated wood supplier, as some treated wood chemical suppliers have clarified their hot dip galvanized recommendation, and do include G185 in their recommendation." Simpson states that "uncoated and painted products should not be used with treated woods." The hot dip galvanizing process to ASTM A153 on our anchor bolts (1.25 ounces of zinc per square foot) EXCEEDS the recent suggestion to meet the G185 Coating Designation for sheets of metal (1.85 ounces of zinc per square foot on both sides of the sheet metal combined). |