Zinc Yellow Trivalent Coated ASTM A193 B7 / A194 2H Stud Bolt Kits Supplied to Project Schedule

Overview

A project client specified zinc yellow trivalent chromate passivated ASTM A193 B7 stud bolts with matching ASTM A194 Grade 2H heavy hex nuts. Trivalent chromium passivation was mandatory because hexavalent chromate is restricted under the client's RoHS-aligned material policy while the yellow visual finish still had to be retained for quick field identification.

Challenge

Trivalent yellow passivate is thinner and less forgiving than legacy hexavalent chromate, so plating had to be tightly controlled to deliver corrosion performance without hydrogen embrittlement risk on quenched and tempered B7. Kits also had to arrive matched, so studs and nuts could not be plated or picked as loose commodity items.

Solution

EMG plated the studs and nuts on a controlled Fe/Zn trivalent line with post-plate baking to relieve hydrogen embrittlement risk, then verified nut assembly by hand-running each pair before packing. Every stud was sleeved in protective mesh with its two nuts kept as a matched kit and cartoned by size so the site received ready-to-install assemblies rather than bulk components.

Results

• Hexavalent-free trivalent finish accepted against the client's material policy
• Post-plate baking applied to eliminate hydrogen embrittlement risk
• Matched, individually sleeved kits — no site sorting required
• Delivered complete to project schedule with no shortfalls

Compliance & Documentation

EN 10204 Type 3.1 mill certification for studs and nuts with heat number traceability, plus zinc plating and trivalent passivation certificates confirming coating thickness and hexavalent-free chemistry, and post-plate baking records.

Products Supplied

• ASTM A193 B7 Stud Bolts
• ASTM A194 2H Heavy Hex Nuts
• Zinc Trivalent and Coated Fastener Systems