Corrosion is the enemy of metal components. The elevated corrosion resistance of nickel alloys is just one reason they’re an outstanding choice for critical, high-stress and/or high-temperature applications where component failure can prove catastrophic. But even among this top-performing group, some alloys stand out. Today we’re taking a look at two very similar alloys that have been specially formulated to resist corrosion: INCONEL alloy 22 and alloy C276.
Corrosion: A Major Threat to Metal Components
Corrosion poses a significant risk to metal components, making it essential to choose materials that resist it effectively. Nickel alloys are particularly renowned for their elevated corrosion resistance, making them ideal for critical applications where high stress and temperatures are involved, as component failure can have catastrophic consequences. Among these high-performing alloys, INCONEL alloy 22 and alloy C276 stand out for their exceptional resistance to corrosion.
Understanding Corrosion
At its core, corrosion occurs when metal oxidizes due to exposure to harsh substances, leading to deterioration, brittleness, and eventual failure. It is a leading cause of component failure, particularly in critical sectors like waste management, nuclear energy, and aerospace, where the implications can be both costly and dangerous.
Preventing and predicting corrosion is complex due to the multitude of influencing factors. Various oxidizing agents—including chlorine, oxygen, and hydrogen peroxide—along with acids such as hydrochloric and sulfuric, can contribute to corrosion. Additionally, heat and contaminants can exacerbate the process, often without detection.
The Corrosion Resistance of Nickel Alloys
Nickel alloys exhibit remarkable corrosion resistance, primarily due to their ability to form a protective layer of nickel oxide when exposed to corrosive media. This layer mitigates further damage, maintaining its effectiveness even at high temperatures—an impressive characteristic of nickel alloys.
Comparing Alloys 22 and C276: The Role of Chromium
Alloys 22 and C276 share many similarities; both are nickel-molybdenum-chromium alloys known for their outstanding anti-corrosion properties across various media and temperatures. They are both excellent choices for applications involving extreme heat and harsh chemicals, including flue gas desulfurization, waste fluid treatment, chemical processing, and pulp & paper manufacturing.
A key component of their corrosion resistance is chromium, which enhances the alloys' inherent protective qualities in a manner akin to nickel. Upon exposure to oxygen, chromium reacts to form a stable, non-reactive layer of chromium oxide that safeguards the alloy from chemical interactions, providing an additional barrier against corrosion.
This is why all stainless steels contain a minimum of 10–11% chromium. Alloy 22 contains a higher percentage at 22%–22.5%, whereas alloy C276 has 14.5%–16.5%. This difference in chromium content is a significant factor in their performance in corrosive environments and highlights one of the main distinctions between the two alloys.
