A. Chris Paterson, an engineer in Simpson Strong-Tie’s research and development department, responds: Because new wood preservatives such as ACQ-D and CA-B are roughly twice as corrosive as CCA-C, galvanized metal connectors and fasteners used with PT wood require thicker protective zinc coatings. So in addition to offering “continuous” G90 hot-dip galvanized coatings (where a layer of zinc is applied to both sides of sheet steel at a coating weight of 0.90 ounce of zinc per square foot) for its standard products and G185 (1.85 oz/ft² of zinc) coatings for its ZMAX connectors and fasteners, Simpson sells post hot-dip galvanized HDG connectors with approximately 2.0 oz/ft² zinc coatings.
In the continuous hot-dip galvanizing process, coil and sheet steel is coated with molten zinc prior to fabrication. Post hot-dip galvanized products are dipped in a molten zinc bath after they have been fabricated.
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