Bolts, nuts, screws, and washers where thicker coatings would clog the threads.
Zinc protects iron and steel through two distinct mechanisms: Barrier Protection
DIN 50961 has close relationships with other national and international standards:
Achieving compliance with DIN 50961 Fe Zn 8b requires a precise, multi-step electroplating process: din 50961 fe zn 8b
The 'B' indicates the type of post-treatment, or passivation, applied after the zinc plating:
The longevity of a zinc coating is directly proportional to its thickness and the efficacy of its passivation layer. Salt Spray Test Performance
To certify that a batch meets , manufacturers perform the following tests: Bolts, nuts, screws, and washers where thicker coatings
| Code | Treatment | Color | Corrosion resistance (Salt spray to red rust) | |------|-----------|-------|------------------------------------------------| | | Blue passivation (thin, transparent) | Iridescent blue-clear | ~12-24 hours | | c | Yellow passivation (hexavalent Cr⁶⁺, historic) | Iridescent yellow | ~96-120 hours | | d | Thick-layer olive drab | Olive green | ~200+ hours | | e | Black passivation | Black | Variable |
This number defines the minimum coating thickness in micrometers (
It provides a baseline level of protection against "white rust" (zinc corrosion products). The Corrosion Protection Mechanism The Corrosion Protection Mechanism | Passivation Type (Code)
| Passivation Type (Code) | Time to White Rust (Zinc Corrosion) | Time to Red Rust (Steel Corrosion) | |------------------------|--------------------------------------|--------------------------------------| | | 6 – 12 hours | 48 – 72 hours | | Yellow (c) | 48 – 96 hours | 120 – 200 hours | | Olive-drab (d) | 120+ hours | 200+ hours |
The technical code acts as a recipe for metal finishers. Each segment provides a critical instruction regarding the composition and performance of the protective layer. 1. Base Material ( Fe )
The "8" refers to the minimum local thickness on significant surfaces. Average thickness is typically higher (9–12 µm), and edges may be thicker due to current concentration.
When you order a part specified as DIN 50961 Fe/Zn 8b , you are getting a steel part with an 8µm electroplated zinc coating and a clear/blue passivation . It is the sweet spot for general mechanical engineering and automotive interiors where cost-effectiveness meets solid corrosion protection.