Cross-group finish comparison
Hot-Dip Galvanizing vs Sherardized Zinc Coating
Hot-Dip Galvanizing (electroplating & electroless plating) and Sherardized Zinc Coating (anodizing & conversion coatings) solve the same problem by different routes; sherardizing is the harder surface (250–400 HV vs 70–250 HV).
Hot-Dip Galvanizing
Electroplating & electroless plating · $$ · instant quote
Hot-dip galvanizing immerses fabricated steel or hardware in molten zinc to form a thick sacrificial alloy coating.
Sherardized Zinc Coating
Anodizing & conversion coatings · $$$
Sherardizing is a thermal-diffusion zinc treatment for steel fasteners and small components, standardized by ASTM A1059.
When to choose which
Choose Hot-dip zinc
Choose Hot-dip zinc when a thicker outdoor structural coating is acceptable.
- Thick sacrificial protection for outdoor steel
- Covers edges and accessible interiors
- Metallurgically bonded iron-zinc alloy layers
Choose Sherardizing
Sherardizing is the pick when its strengths below matter more than Hot-dip zinc's.
- Uniform 15–75 µm diffusion coating
- Good thread and recess coverage
- Sacrificial zinc corrosion protection
What the numbers say
- Sherardizing is the harder surface (250–400 HV vs 70–250 HV).
- Hot-dip zinc is the lower-cost option ($$).
- Sherardizing is the thinner coating (15–75 µm), so it disturbs tight fits less.
- Sherardizing tolerates more heat (250 °C continuous).
Scores side by side
Each score is 0–100 against every finish in this catalog. Corrosion is derived from salt-spray test duration and surface hardness from the finish layer's Vickers hardness where a measured figure exists; a finish that leaves the base metal's own surface is not rated for hardness. Cosmetic, lubricity and cost are FabDigit's engineering assessment. Scores and typical figures are screening data, not matched side-by-side tests or service-life rankings; ASTM B117 is a controlled salt-fog method, not a field-life prediction.
| Score | Hot-dip zinc | Sherardizing |
|---|---|---|
| Corrosion resistance | 90 Excellent | 83 Very good |
| Surface hardness / wear | 42 Fair | 56 Good |
| Cosmetic quality | 32 Low | 30 Low |
| Lubricity | 22 Low | 30 Low |
| Cost | 28 $$ | 58 $$$ |
Key numbers
| Property | Hot-dip zinc | Sherardizing |
|---|---|---|
| Thickness | 45–100 µm | 15–75 µm |
| Surface hardness | 70–250 HV | 250–400 HV |
| Salt-spray test duration | 800–1,500 h | 500–1,000 h |
| Max service temperature | 200 °C | 250 °C |
| Electrical | Conductive | Conductive |
| Colours | silver gray, matte gray | matte grey |
| Relative cost | Standard ($$) | Premium ($$$) |
| Added lead time | 4–10 working days | 7–15 working days |
| RoHS | Compliant | Compliant |
| Instant quote | Yes | On request |
Bold marks the side that is ahead on a row where more (or less, for cost and lead time) is better. Ranges are the typical specification window; the drawing call-out fixes the class.
Which materials take each finish
| Material family | Hot-dip zinc | Sherardizing |
|---|---|---|
| Steel | Yes | Yes |
| DMLS / SLM | No | With care |
Specifications and drawing call-outs
Hot-dip zinc
- ASTM A123 — Standard Specification for Zinc (Hot-Dip Galvanized) Coatings on Iron and Steel Products
- ASTM A153 — Standard Specification for Zinc Coating (Hot-Dip) on Iron and Steel Hardware
HOT-DIP GALVANIZE AFTER FABRICATION PER ASTM A123; PROVIDE VENT AND DRAIN HOLES; CHASE M12 THREADS AFTER GALVANIZING
Sherardizing
No governing public specification — called out by name and thickness.
SHERARDIZE STEEL PARTS PER ASTM A1059, CLASS 30, 30 µm MINIMUM COATING THICKNESS; APPLY TRIVALENT PASSIVATION; THREADS SHALL ACCEPT GO GAUGE AFTER COATING
Hot-dip zinc vs Sherardizing — frequently asked
What is the difference between Hot-dip zinc and Sherardizing?
Hot-Dip Galvanizing (electroplating & electroless plating) and Sherardized Zinc Coating (anodizing & conversion coatings) solve the same problem by different routes; sherardizing is the harder surface (250–400 HV vs 70–250 HV). Hot-dip zinc is the lower-cost option ($$). Sherardizing is the thinner coating (15–75 µm), so it disturbs tight fits less.
When should I use Hot-dip zinc instead of Sherardizing?
Choose Hot-dip zinc when a thicker outdoor structural coating is acceptable.
Is Hot-dip zinc or Sherardizing cheaper?
Hot-dip zinc is the lower-cost finish ($$ against $$$ for Sherardizing) 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 Sherardizing?
Hot-dip zinc. Hot-dip zinc is rated 800–1,500 h and Sherardizing 500–1,000 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.