Zinc plating vs galvanizing: which corrosion finish?
Zinc plating vs hot-dip galvanizing: coating thickness, corrosion life, cost, appearance and threads, and how to choose for indoor vs outdoor steel.
Both coat steel in zinc to stop rust, but the process and the life are very different. Electroplated zinc is thin (5 to 25 microns), smooth, cheap and good for indoor or light-duty parts and fasteners. Hot-dip galvanizing dunks the part in molten zinc for a thick (45 to 100+ micron) metallurgically bonded coating that lasts decades outdoors. Indoors or cosmetic and threaded: zinc plate. Outdoors, structural, or buried: hot-dip galvanize.
Same metal, very different process
Both rely on zinc sacrificing itself to protect the steel underneath. The difference is how much zinc you get and how it bonds.
| Zinc plating (electroplated) | Hot-dip galvanizing | |
|---|---|---|
| Process | Zinc deposited electrochemically | Dipped in molten zinc (~450 C) |
| Thickness | 5 to 25 microns | 45 to 100+ microns |
| Corrosion life | Months to a few years outdoors | Decades outdoors |
| Finish | Smooth, bright, even | Rougher, matte, with a spangle |
| Threads | Keeps thread fit | Can clog fine threads |
| Cost | Lower per part | Higher, but priced by weight |
| Best for | Indoor parts, fasteners, cosmetic | Structural steel, outdoor, buried |
When zinc plating wins
Indoor hardware, fasteners and small parts, electrical enclosures, and anything where a smooth even finish and precise thread fit matter. Plating is thin enough that it does not change dimensions much, and it takes a clear or coloured chromate (or the newer trivalent passivates) for extra corrosion life and appearance. For true outdoor life, plating alone is not enough.
When hot-dip galvanizing wins
Structural steel, railings, fencing, trailers, agricultural and outdoor equipment, and anything that lives in weather or soil. The thick, metallurgically bonded coating takes abuse and self-heals small scratches because the surrounding zinc keeps protecting the exposed steel. For a road-salt province, galvanizing (or galvanizing then powder coat, a duplex system) is what survives the winter. See hot-dip galvanizing and powder coat vs galvanizing.
Threads, dimensions and masking
Hot-dip is thick enough to clog fine threads, so fasteners are often centrifuged, or threads are cut oversize or chased after dipping. Plating is thin and keeps thread fit, which is one reason most plated fasteners are electroplated zinc. Tell the shop which surfaces are critical so they mask or chase them.
What to send for a quote
The part and base material, the environment (indoor, outdoor, marine, buried), any thread or dimensional limits, and the spec if you have one (ASTM B633 for zinc plating, ASTM A123 or A153 for hot-dip). Request quotes from Canadian plating and galvanizing shops.
FAQ
What is the difference between zinc plating and galvanizing?
Both coat steel in zinc. Zinc plating is a thin electroplated layer for indoor and light-duty parts; hot-dip galvanizing is a thick molten-zinc coating for long outdoor life.
Which lasts longer, zinc plating or hot-dip galvanizing?
Hot-dip galvanizing, by a wide margin. Its coating is several times thicker, so it protects steel outdoors for decades where thin zinc plating lasts months to a few years.
Can you galvanize threaded fasteners?
Yes, but the thick coating can clog fine threads, so hot-dip fasteners are centrifuged or the threads are cut oversize. For precise thread fit, electroplated zinc is the common choice.
Is zinc plating cheaper than galvanizing?
Per part, plating is usually cheaper and gives a smoother finish. Galvanizing costs more but buys far longer outdoor life, so the right choice depends on the environment.
What is the best finish for outdoor steel in a salt climate?
Hot-dip galvanizing, or galvanizing followed by powder coat (a duplex system). One thin coating does not survive repeated road-salt exposure.
Last reviewed: October 2026. Related reading: powder coat vs hot-dip galvanizing and electroplating: a buyer's guide.
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