Sulfidation
Hot sulfidation is a chemical attack on metals by sulfur gas at high temperatures, forming brittle metal sulfides and impairing mechanical properties.
Physicochemical Mechanism of Action
Hot sulfidation occurs when sulfur-containing gases (e.g., sulfur dioxide) come into contact with metals at high temperatures. The sulfur reacts with the metal to form brittle metal sulfides. This process can be understood through the chemical reaction between sulfur and metal ions such as iron (Fe): Fe + S → FeS.
Metallurgical Relevance & Risks in Welding
Hot sulfidation leads to a change in the metal that impairs its mechanical properties. The formed brittle metal sulfides can reduce hardness and strength, leading to lower toughness and increased susceptibility to cracking. This can occur particularly at high temperatures and in environments with high sulfur content.
Workshop Practice & Action Instructions
To avoid hot sulfidation, the following measures should be taken:
• Use shielding gases such as argon or helium when welding in environments with high sulfur content.
• Ensure the workshop is well-ventilated and sulfur-containing gases are excluded.
• Select metals with low susceptibility to sulfidation or pre-treat the metal accordingly before welding.