Coatings & Corrosion Selection
Printable shop wall chart: Coatings & Corrosion Selection. Free letter-size PDF to print and post at the counter; 25 x 36 inch poster version available.
| Finish | Thickness (typical) | Best for | Watch out |
|---|---|---|---|
| Plain / oil | None | Indoor, painted later | Rusts |
| Zinc plate (F1941) | 5 - 8 micrometres | Indoor, mild | Hydrogen embrittlement on hard parts |
| Hot-dip galvanized (F2329) | 50+ micrometres | Outdoor structural | Oversize nuts; not A490 |
| Mechanical zinc (B695) | By class | Structural, hard parts | Matte appearance |
| Zinc flake (F3393) | 6 - 12 micrometres | Automotive, A490 | Thin; coating damage |
| Black oxide | Very thin | Appearance, sockets | Little corrosion protection |
A coating never changes the grade. It does change friction, so it changes the torque needed. Hydrogen embrittlement risk rises sharply above about HRC 39.
These tables carry the same figures as the printed sheet below.
The printed sheet

25 x 36 inch poster version
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Text version of this sheet
CLEAR ZINC
YELLOW ZINC
BLACK OXIDE
HOT-DIP GALV
ZINC FLAKE
Common fastener finishes · thickness, best use and cautions
Common finishes
Finish
Thickness (typical)
Best for
Watch out
Plain / oil
None
Indoor, painted later
Rusts
Zinc plate (F1941)
5 - 8 micrometres
Indoor, mild
Hydrogen embrittlement on hard parts
Hot-dip galvanized (F2329)
50+ micrometres
Outdoor structural
Oversize nuts; not A490
Mechanical zinc (B695)
By class
Structural, hard parts
Matte appearance
Zinc flake (F3393)
6 - 12 micrometres
Automotive, A490
Thin; coating damage
Black oxide
Very thin
Appearance, sockets
Little corrosion protection
A coating never changes the grade. It does change friction, so it changes the torque needed. Hydrogen embrittlement risk rises sharply above about HRC 39.
The Fastener App | TheFastenerApp.com
Fastener Guide reference FG-33828C · thefastenerapp.com/fastener-guide/wall-charts/coatings-and-corrosion-selection · © The Fastener App. Reference only — verify the current governing standard, drawing and manufacturer data before specifying or installing.

























