COLD ~ HOT DIP GALVANIZING
COLD ~ HOT DIP GALVANIZING
(OP)
Are both ways of galvanizing equally good?
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COLD ~ HOT DIP GALVANIZING
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RE: COLD ~ HOT DIP GALVANIZING
Better with respect to abrasion, appearance, bearing surface in a bolted connection, chromating, corrosion resistance (where & from what...?), cost, ease of removal prior to welding, embrittlement risk, field application, flexibility...?
Is the application a fastener, sheet or structural member?
“Cold galvanizing” often refers to application of a zinc-rich paint.
Perhaps you meant either mechanical plating or electroplating? If so, which? To what specification?
Please furnish details.
RE: COLD ~ HOT DIP GALVANIZING
RE: COLD ~ HOT DIP GALVANIZING
In our work, we galvanize miscellaneous items, and use "cold galvanizing compound" to touch up miscellaneous field welds. It is indeed a paint product, with appearance similar to the galvanizing. It's not intended to replace galvanizing, just for those types of applications where you can't galvanize.
I see ads for "cold welding" compound...IE, epoxy cement, as well.
RE: COLD ~ HOT DIP GALVANIZING
The coatings conform to MIL-P-21035B PAINT HIGH ZINC DUST CONTENT, GALVANIZING REPAIR, which makes them zinc-rich paints rather than “galvanizing” IMHO.
Better corrosion resistance than with MIL-P-21035B paint can be obtained with Dacromet®. This could be considered a “Warm Galvanizing” coating or more properly “Warm Galvalume,” since it also contains aluminum. From http://www.dacromet.com/hcoat.htm
“Our coating compositions are proprietary water based coating dispersions containing metal oxides, metallic zinc and aluminum flakes. The zinc and aluminum platelets align in multiple layers forming a metallic silver gray coating. Applied as a liquid material, the coating becomes totally inorganic after curing at 610° F/321°C.”
As the cure temperature is only 51oC below the Al-Zn eutectic, and especially with some proprietary additives present, I would expect some significant sintering during the cure.
In addition to the “cold galvanizing” field repairs of HDG mentioned by JStephen, there are also hot methods for applying molten zinc to a cleaned surface: Thermal spray is used for large areas and “hot stick” for small. The latter is essentially soldering: heating a fluxed area with a torch and then applying stick zinc alloy such as Galvaguard®. For more information, Industrial Galvanizers' website is very informative on HDG, and also compares the various types of zinc coatings:
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RE: COLD ~ HOT DIP GALVANIZING
Hot dipping provides a harder more abrasion resistant surface though. With hot dipping you have to be concerned about possible thermal distortions, like if you have a thin plate welded to something more massive. I have seen this result in the thin plate buckling and welds breaking. The American Galvanizers Association has some good material on their website regarding hot dipping, and welding to galvanized steel.
RE: COLD ~ HOT DIP GALVANIZING
RE: COLD ~ HOT DIP GALVANIZING
I've been told that you should not galvanize anything that is embedded in concrete.
RE: COLD ~ HOT DIP GALVANIZING
If you were embeding something that was aluminized or had aluminum that would be a problem. The alkalinity of concrete attacks aluminum, and if you have aluminum in contact with embeddes steel in concrete you can get aggressive corrosion of the aluminum.
RE: COLD ~ HOT DIP GALVANIZING
RE: COLD ~ HOT DIP GALVANIZING
Cold galvanizing can be either a zinc-rich paint or an electroplating process. Electroplated zinc is a good process; however, the zinc layer is much thinner than with HDG.
Zinc-rich paints are nice coatings, but they are only coatings and don't offer the same type of long-term sacrificial corrosion protection that either HDG or electroplating will provide.
RE: COLD ~ HOT DIP GALVANIZING