8b | Din 50961 Fe Zn
This specifies the coating material. "Zn" stands for Zinc , meaning the protective layer is applied via electrogalvanizing (zinc electroplating).
However, ISO 2081 no longer ties specific corrosion resistance to color; you must specify required hours to white/red rust separately (e.g., "≥12 h to white rust").
This is the German standard (Deutsches Institut für Normung) titled .
Some specifications add a top organic or inorganic sealer to enhance corrosion resistance, though this is not required for "8b." din 50961 fe zn 8b
While hot-dip galvanizing can be 10x thicker, it is often too bulky for precision parts. is the "sweet spot" for: Automotive fasteners and brackets.
In the world of metal finishing and surface treatment, standards play a crucial role in ensuring quality, corrosion resistance, and durability. One such designation frequently encountered in engineering drawings and manufacturing specifications is . This standard, while partially superseded by modern ISO standards, remains a foundational guideline for zinc electroplating on steel.
| 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 specifies the coating material
DIN 50961 has been largely superseded by DIN EN ISO 4042 (for fasteners) and DIN EN 12329 (for general steel parts). However, many legacy drawings and specifications still reference DIN 50961. When converting, Fe/Zn 8b is typically equivalent to Fe/Zn 8c2C (with Cr(III) passivation) under the newer standards.
: After the zinc layer is set, the part receives a "b" treatment—a chromate conversion coating
This specification is very common for:
refers to the type of "passivation" or chromate conversion coating applied over the zinc. In the DIN 50961 system: is clear/blue (transparent). iridescent/yellow is olive green.
Although Germany has largely adopted international standards like ISO 2081 (Zinc plating on iron/steel) and ISO 9227 (Salt spray testing), DIN 50961 remains widely used across Central Europe, particularly in the automotive, machinery, and fastener industries. The standard defines: