Metallization

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Author Message Gary Barnett New member Username: gary_barnett Post Number: 1 Registered: 08-2011 Posted on Wednesday, May 07, 2014 - 01:49 am:    I have a new client who has reviewed our specification and requested that we replace references to "galvanizing" with "metallizing." I am unfamiliar with this process. In searching the internet, I found a fabricator which had this definition of Metallization: "Metallizing is considered a cold process in that the aluminum or zinc is deposited onto steel by spraying rather than by dipping the steel into a bath of molten zinc as with galvanizing. The steel remains relatively cool at about 250º-300ºF. There is virtually no risk of heat distortion or weld damage by metallizing." In anyone familiar with this process and can advise me where to find the corrosion resistance of this process verses galvanizing? Your help is appreciated. Mark Gilligan SE, Senior Member Username: mark_gilligan Post Number: 662 Registered: 10-2007 Posted on Wednesday, May 07, 2014 - 12:53 pm:    The amount of corrosion resistance is related to the amount of zinc deposited. Galvanizing results in a thicker zinc layer. anon (Unregistered Guest) Unregistered guest Posted on Wednesday, May 07, 2014 - 01:15 pm:    You might take a look at ASTM A 780. This is the galvanizing repair standard you will find in probably every Project Manual ever written within the last couple decades. This ASTM standard describes three ways to make the repair - zinc-rich paint, zinc solder, and metallizing. Might be some good info for you in this standard. Ellis C. Whitby, PE, CSI, AIA, LEED® AP Senior Member Username: ecwhitby Post Number: 218 Registered: 03-2003 Posted on Wednesday, May 07, 2014 - 01:57 pm:    ASTM A123, Standard Specification for Zinc (Hot-Dip Galvanized) Coatings on Iron and Steel Products ASTM A653, Standard Specification for Steel Sheet, Zinc-Coated (Galvanized) or Zinc-Iron Alloy-Coated (Galvannealed) by the Hot-Dip Process ASTM A780, Standard Practice for Repair of Damaged and Uncoated Areas of Hot-Dip Galvanized Coatings John Bunzick, CCS, CCCA, LEED AP Senior Member Username: bunzick Post Number: 1571 Registered: 03-2002 Posted on Wednesday, May 07, 2014 - 02:18 pm:    My understanding of this process is that it is mostly used where hot-dipping is impossible, or at least impracticable. A prime example may be coating an in-place steel bridge. I don't know whether the zinc alloy is more likely to lose adhesion than hot dipping, but I do know that the temperatures involved in hot-dipping cause metallurgical changes at the interface between the zinc and the steel substrate. I don't think you would have this effect with metallization because I doubt the substrate gets very hot. Gary Barnett Junior Member Username: gary_barnett Post Number: 2 Registered: 08-2011 Posted on Thursday, May 08, 2014 - 01:50 pm:    Thanks for your help, Ellis, do you know of any ASTM's for the Metallization? John, The process as described to me is to heat the item to be sprayed up to 250-350 degrees F prior to spraying. I found a comparison sheet published by the HD Galvanizer's indicating that a HD Galvanized item will last 50+ years in an aggressive marine environment while a metallized item will last 17 years. I talked to an metallizer applicator and he indicated that they have objects that show no sign of corrosion in 19 years close to the ocean. The Architect is not familiar with this system either but he wants to follow the owner's direction in this instance. Ellis C. Whitby, PE, CSI, AIA, LEED® AP Senior Member Username: ecwhitby Post Number: 220 Registered: 03-2003 Posted on Thursday, May 08, 2014 - 04:16 pm:    Unfortunately I only know of it being listed as part of ASTM A780. I have never used it for new work. Ellis C. Whitby, PE, CSI, AIA, LEED® AP Senior Member Username: ecwhitby Post Number: 221 Registered: 03-2003 Posted on Thursday, May 08, 2014 - 04:20 pm:    I came across this (note: I cannot vouch for its accuracy and veracity): http://www.galvanizeit.org/education-and-resources/publications/hot-dip-galvanized-steel-vs-zinc-spray-metallizing-2008