Home Categories Send inquiry

What are the surface treatment methods for B7 threaded rods?

B7 is a chromium-molybdenum alloy steel; as it is prone to rusting, it almost invariably requires surface treatment.
The most common surface treatments for B7 fasteners in engineering applications are as follows:

1. Black Oxide / Black Phosphate

Appearance: Matte black
Characteristics: Low cost, moderate rust resistance, high-temperature resistant
Applications: Indoor use, dry environments, high-temperature equipment

Black-Oxide-b7-threaded-rod

2. Electro-Galvanizing (Zinc Plating)

Appearance: Silvery-white / Iridescent (Colored)
Characteristics: Moderate rust resistance, moderate cost
Note: B7 high-strength steel is susceptible to hydrogen embrittlement; a post-plating hydrogen embrittlement relief treatment is typically required.

https://www.fixdex.com/class-12-9-steel-threaded-rods-product/

3. Hot Dip Galvanizing (HDG)

Appearance: Thick, bright silver layer / Grayish finish
Characteristics: Extremely strong rust resistance; suitable for outdoor, coastal, and bridge applications
Note: The zinc layer is thick, which increases the thread diameter; oversized holes are often specified, or oversized nuts are used for mating.

https://www.fixdex.com/threaded-rod-sizes-carbon-steel-din975-product/

4. Teflon / PTFE Coating (Xylan, PTFE Coated)

Appearance: Gray, green, blue, etc.
Characteristics: Superior corrosion resistance, acid/alkali resistant, non-stick, low friction
Applications: Petrochemical industry, offshore platforms, desulfurization systems, environments with strong acids/alkalis
Commonly used in high-end projects.

https://www.fixdex.com/wholesale-xylan-coated-threaded-rods-stud-bolt-product/

 

5. Dacromet / Zinc-Aluminum Coating (DACROMET / Geomet)

Appearance: Silvery-gray
Characteristics: No risk of hydrogen embrittlement, high corrosion resistance, high-temperature resistant
Applications: Automotive industry, wind power, high-end steel structures; serves as an alternative to electro-galvanizing.

https://www.fixdex.com/hdg-threaded-rod-product/

6. Mechanical Galvanizing

Characteristics: No risk of hydrogen embrittlement, good corrosion resistance
Applications: High-strength fasteners that are sensitive to hydrogen embrittlement.

7. Cadmium Plating

Characteristics: Excellent corrosion resistance; however, it is toxic and subject to environmental restrictions.
It has now been largely replaced by Teflon or Dacromet coatings.