Hydrogen removal after fastener plating is a critical post-treatment process, primarily due to the risk of hydrogen embrittlement—a phenomenon that can lead to catastrophic fastener failure, especially in high-strength materials. Here’s why it’s important and how it’s typically addressed:
Author: Robby
Hydrogen removal after fastener plating is a critical post-treatment process, primarily due to the risk of hydrogen embrittlement—a phenomenon that can lead to catastrophic fastener failure, especially in high-strength materials. Here’s why it’s important and how it’s typically addressed:
Hydrogen Embrittlement: During plating (e.g., cadmium, zinc, or chrome plating), hydrogen atoms can diffuse into the steel, making it brittle and prone to cracking under stress.
Delayed Failure: Embrittlement may not be immediate; failures can occur hours or days after plating, particularly under tensile loads.
High-Strength Steel Vulnerability: Fasteners with tensile strengths above 1,000 MPa (e.g., Grade 8, 10.9, 12.9) are especially susceptible.
Baking (Heat Treatment):
Typical Process: Heating fasteners at 190–220°C (375–430°F) for 4–24 hours (varies by material and plating type).
Purpose: Allows trapped hydrogen to diffuse out of the metal.
Timing: Must be done within 1–4 hours after plating to prevent hydrogen migration into critical areas.
Alternative Methods:
Mechanical Vibration (less common, limited effectiveness).
Room Temperature Aging (slower, less reliable than baking).
ASTM B850: Specifies requirements for hydrogen embrittlement relief.
ISO 9587: Covers hydrogen embrittlement relief for fasteners.
Military & Aerospace Standards (e.g., AMS 2759, NADCAP AC7102) often mandate strict baking protocols.
Sudden Fracture: Fasteners may snap under load without visible deformation.
Reduced Fatigue Life: Hydrogen-induced cracks propagate faster under cyclic loads.
Safety Risks: Critical applications (e.g., automotive, aerospace, construction) face severe liability if fasteners fail.
Low-strength fasteners (e.g., Grade 2, A307).
Non-ferrous fasteners (e.g., stainless steel, aluminum, titanium).
Plating processes with minimal hydrogen generation (e.g., mechanical zinc plating).
Hydrogen removal is essential for plated high-strength fasteners to ensure long-term reliability and safety. Proper baking procedures must follow industry standards to mitigate embrittlement risks. Neglecting this step can lead to premature failures, particularly in critical structural applications.