Plating & metallizing · finish comparison
Hot-Dip Galvanizing vs Zinc Plating
Hot-Dip Galvanizing and Zinc Plating are both electroplating & electroless plating finishes; hot-dip zinc resists corrosion better (800–1,500 h vs 96–300 h salt spray).
Hot-Dip Galvanizing
Electroplating & electroless plating · $$ · instant quote
Hot-dip galvanizing immerses fabricated steel or hardware in molten zinc to form a thick sacrificial alloy coating.
Zinc Plating
Electroplating & electroless plating · $ · instant quote
Electrolytic zinc is a thin sacrificial coating for carbon steel hardware and parts.
When to choose which
Choose Hot-dip zinc
Choose Hot-dip zinc when a much thicker outdoor coating is acceptable.
- Thick sacrificial protection for outdoor steel
- Covers edges and accessible interiors
- Metallurgically bonded iron-zinc alloy layers
Choose Zinc plate
Choose Zinc plate when threads and precision dimensions require a 5–25 µm coating.
- Low-cost sacrificial protection for steel
- SC1–SC4 provide 5, 8, 13, or 25 µm minimum zinc
- Rack or barrel processing supports both precision parts and fasteners
What the numbers say
- Hot-dip zinc resists corrosion better (800–1,500 h vs 96–300 h salt spray).
- Hot-dip zinc is the harder surface (70–250 HV vs 40–100 HV).
- Zinc plate is the lower-cost option ($).
- Zinc plate is the thinner coating (5–25 µm), so it disturbs tight fits less.
- Hot-dip zinc tolerates more heat (200 °C continuous).
Buyer's decision notes
Hot-dip galvanizing fits fabricated structural steel and hardware that need a rugged zinc coating and can tolerate immersion, heat and a comparatively heavy finish. Electroplated zinc fits smaller precision steel parts and fasteners that need a controlled plated coating, conversion finish and tighter interface plan.
- Product scope
- ASTM A123 covers fabricated and unfabricated iron and steel products; centrifuged hardware belongs under ASTM A153. ASTM B633 covers electrodeposited zinc on iron and steel. Select the document by the product form and process, not by writing only “galvanized.”
- Geometry and fit
- Hot-dip parts need venting, drainage and allowance for zinc on threads, holes and mating faces. Zinc plate offers finer dimensional control, but thickness still varies with current distribution. In both cases, call out final fit and significant surfaces separately from coating thickness.
- Fabrication sequence
- Review welds, overlapping surfaces, sealed cavities and distortion risk before hot dipping. For electrozinc, identify masking, rack contact and the conversion coating or sealer after plating.
- Exposure evidence
- Zinc mass, continuity, environment and damage determine sacrificial protection. Neutral salt spray is useful for qualification and process comparison, but it is not a direct conversion to years outdoors or performance in a galvanic joint.
Put this on the RFQ
- State ASTM A123 or A153 for hot dip, or ASTM B633 for electroplated zinc, with the applicable class, type and post-treatment.
- For hot dip, include steel chemistry where required, assembly drawings, vent and drain details, thread allowance and distortion-sensitive features.
- For zinc plate, mark significant surfaces, contacts, threads and masking, plus hydrogen-embrittlement controls for susceptible steels.
Primary references
- ASTM — A123/A123M — Active specification for hot-dip zinc coatings on fabricated and unfabricated iron and steel products.
- ASTM — B633 — Active specification for electrodeposited zinc coatings on iron and steel.
FabDigit resources: Hot-dip zinc datasheet · Zinc plate datasheet · surface finish selection guide
Scores side by side
Each score is 0–100 against every finish in this catalog. Corrosion is derived from salt-spray test duration and surface hardness from the finish layer's Vickers hardness where a measured figure exists; a finish that leaves the base metal's own surface is not rated for hardness. Cosmetic, lubricity and cost are FabDigit's engineering assessment. Scores and typical figures are screening data, not matched side-by-side tests or service-life rankings; ASTM B117 is a controlled salt-fog method, not a field-life prediction.
| Score | Hot-dip zinc | Zinc plate |
|---|---|---|
| Corrosion resistance | 90 Excellent | 60 Good |
| Surface hardness / wear | 42 Fair | 30 Low |
| Cosmetic quality | 32 Low | 55 Good |
| Lubricity | 22 Low | 25 Low |
| Cost | 28 $$ | 12 $ |
Key numbers
| Property | Hot-dip zinc | Zinc plate |
|---|---|---|
| Thickness | 45–100 µm | 5–25 µm |
| Surface hardness | 70–250 HV | 40–100 HV |
| Salt-spray test duration | 800–1,500 h | 96–300 h |
| Max service temperature | 200 °C | 80 °C |
| Electrical | Conductive | Conductive |
| Colours | silver gray, matte gray | clear blue, yellow iridescent, black, olive drab |
| Relative cost | Standard ($$) | Budget ($) |
| Added lead time | 4–10 working days | 2–5 working days |
| RoHS | Compliant | Compliant |
| Instant quote | Yes | Yes |
Bold marks the side that is ahead on a row where more (or less, for cost and lead time) is better. Ranges are the typical specification window; the drawing call-out fixes the class.
Which materials take each finish
| Material family | Hot-dip zinc | Zinc plate |
|---|---|---|
| Steel | Yes | Yes |
| DMLS / SLM | No | With care |
| Aluminum | No | Limited |
| Brass | No | Limited |
| Copper Alloy | No | Limited |
| Stainless Steel | No | Limited |
| Zinc Alloy | No | Limited |
Specifications and drawing call-outs
Hot-dip zinc
- ASTM A123 — Standard Specification for Zinc (Hot-Dip Galvanized) Coatings on Iron and Steel Products
- ASTM A153 — Standard Specification for Zinc Coating (Hot-Dip) on Iron and Steel Hardware
HOT-DIP GALVANIZE AFTER FABRICATION PER ASTM A123; PROVIDE VENT AND DRAIN HOLES; CHASE M12 THREADS AFTER GALVANIZING
Zinc plate
- ASTM B633 — Standard Specification for Electrodeposited Coatings of Zinc on Iron and Steel
ZINC PLATE PER ASTM B633, SC3, TYPE V, CLEAR TRIVALENT PASSIVATE; 13 µm MIN; BAKE PER ASTM B850 WITHIN 1 H OF PLATING
Hot-dip zinc vs Zinc plate — frequently asked
What is the difference between Hot-dip zinc and Zinc plate?
Hot-Dip Galvanizing and Zinc Plating are both electroplating & electroless plating finishes; hot-dip zinc resists corrosion better (800–1,500 h vs 96–300 h salt spray). Hot-dip zinc is the harder surface (70–250 HV vs 40–100 HV). Zinc plate is the lower-cost option ($).
When should I use Hot-dip zinc instead of Zinc plate?
Choose Hot-dip zinc when a much thicker outdoor coating is acceptable. Conversely: choose Zinc plate when threads and precision dimensions require a 5–25 µm coating.
Is Hot-dip zinc or Zinc plate cheaper?
Zinc plate is the lower-cost finish ($ against $$ for Hot-dip zinc) among the finishes FabDigit quotes. Both are priced per part with a lot minimum; the exact figure appears on the instant quote once the part is uploaded.
Which lasts longer in salt spray, Hot-dip zinc or Zinc plate?
Hot-dip zinc. Hot-dip zinc is rated 800–1,500 h and Zinc plate 96–300 h in neutral salt spray (ASTM B117 or the qualification hours of the governing specification). The figures are for the finish as specified on a clean, properly pre-treated substrate; sealing, thickness class and substrate alloy move them.