to red rust in salt spray testing, though specific requirements can vary by application. Application
High-current density areas (outer edges, threads, sharp corners) typically receive thicker layers.
Zinc is less noble than iron on the galvanic series. If the coating is scratched or damaged, exposing the underlying steel, the surrounding zinc sacrifices itself by corroding first. This continuous electrochemical reaction prevents the localized formation of destructive red rust ( Fe2O3cap F e sub 2 cap O sub 3 Coating Thickness Realities
Are you looking to that can fulfill this specific standard? din 50961 fe zn 8b
A brilliant blue surface with a metallic sheen and subtle rainbow iridescence. It is the most visually attractive of all chromate finishes. Corrosion Resistance (Red Rust): According to the standard, Fe Zn 8b must withstand 72 hours in the neutral salt spray test (NSS) before red rust appears (when using Cr(III) based passivations). Electrical Conductivity: The blue film is very thin (approx. 0.1–0.5 µm). Unlike yellow or olive passivations, Fe Zn 8b offers relatively low contact resistance , making it ideal for threaded connections that require electrical grounding (e.g., automotive chassis bolts, electronic enclosures). Weldability: Due to its thin, conductive layer, blue passivated zinc is preferred over thicker coatings for resistance spot welding.
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It is typically suited for indoor environments or sheltered outdoor applications. Thicker coatings (e.g., 12 or 25 to red rust in salt spray testing, though
| Characteristic | | Fe Zn 12c | Fe Zn 8g | | :--- | :--- | :--- | :--- | | Thickness | 8 µm | 12 µm | 8 µm | | Passivation | Blue | Yellow (iridescent) | Clear/Colorless | | Red Rust (NSS) | ~72 hrs | ~120-180 hrs | ~24 hrs | | White Rust Resistance | Poor - 24 hrs | Good - 72 hrs | Poor - 8 hrs | | Contact Resistance | Low | Medium | Very Low | | Typical Use | Threaded fasteners, grounding clips | Brake lines, leaf springs | Appliance covers (cosmetic) |
This article is for informational purposes only. Always consult the full standard documents and your surface treatment specialist for specific application requirements.
Zinc acts as a . Even if the coating is scratched and the underlying steel is exposed, the zinc will corrode first to protect the iron. The "b" (bright) designation usually involves a trivalent or hexavalent chromium passivate that delays the formation of "white rust" (zinc corrosion) before the "red rust" (steel corrosion) ever starts. 3. Why Not Thicker? If the coating is scratched or damaged, exposing
To ensure the zinc and chromate layers are securely bonded, tests such as the or the peel test are conducted. This prevents the coating from flaking or peeling during part assembly or use.
: Specifies an electroplated Zinc coating with a minimum thickness of 8 micrometers ( m) .