Zinc primer performance

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Author Message Jim Brittell, AIA, CSI Unregistered guest Posted on Thursday, March 27, 2003 - 05:07 pm:    We've noticed problems with corrosion at welded areas on hot-dipped galvanized steel guardrails and handrails. The welded areas are treated with zinc primer before painting, but these areas start to corrode within a year. The atmosphere is corrosive (near the ocean). The areas not affected by welding perform well. Does anyone have recommendations on how to correct this? Richard L. Hird Unregistered guest Posted on Thursday, March 27, 2003 - 07:34 pm:    Recommend that you use plain steel, not galvanized, fabricate it fill and grind welds smooth and then hot dip galvanize the complete assembly without any field welds. Aluminum pipe railings are even better in wet environmnets For repairs there used to be a product from ZRC for regalvanizing welds that we would use in Chemical plants. I really do not know if it is any better than the products recommended by your paint manufacturer. Jim Brittell, AIA, CSI Unregistered guest Posted on Friday, March 28, 2003 - 01:31 pm:    Richard: Thanks for the tip. ZRC is still available and they have a very informative web site at www.zrcworldwide.com. One particularly interesting bit of information in their latest newsletter is that ASTM A 780 has just been revised to allow an option for zinc repair compounds to have minimum 92% zinc by weight. Previously, the standard was for 65% or more zinc content. ZRC's products are 93-95% zinc by weight. We have considered aluminum railings. You are right that they are more corrosion-resistant, but they don't stand up to the abuse they get on a college campus. We are now considering type 316/316L stainless steel with an as-drawn finish to minimize maintenance requirements.