Few names in corrosion-resistant alloys are as widely recognized as Hastelloy®. But what does the name actually mean? Who developed the first Hastelloy alloys, and what is the fundamental difference between the B and C series? The answers lie in nearly a century of materials development driven by increasingly demanding industrial environments.
Hastelloy® Is a Brand, Not a Generic Alloy Name
HASTELLOY® is a registered trademark of Haynes International. It is not the generic name for all nickel-based corrosion-resistant alloys. The name was formed from “Haynes Stellite Alloy.”
Elwood Haynes patented a cobalt-based alloy later known as STELLITE® in 1907 and founded Haynes Stellite Works in 1912. The company’s early expertise in specialty alloys laid the groundwork for later development of the Hastelloy family. Frederick M. Becket led important early alloy-development work, and a 1921 patent for nickel-molybdenum alloy compositions helped pave the way for the first Hastelloy grades. The Hastelloy name was coined in 1922.
The First Alloys: A, B, C and D
During the 1920s, the first Hastelloy grades—including A and B—began to address the corrosion problems facing the growing chemical-processing industry. Equipment exposed to acids could fail quickly, and engineers needed materials that could withstand more aggressive service.
The B family was based primarily on nickel and molybdenum. It was developed for strongly reducing environments, especially hydrochloric acid. The C family added chromium to the nickel-molybdenum base. Chromium improved resistance to oxidizing conditions, giving C alloys a broader range of potential applications.
Early alloys had a practical limitation: welding and heat exposure could lead to the formation of undesirable phases and a loss of corrosion resistance in some conditions. Fabrication procedures and, in certain applications, post-weld heat treatment therefore required careful attention.
B Series vs. C Series: The Core Difference
The simplest way to understand the two families is to look at the environments they were designed to handle. B-series alloys are nickel-molybdenum materials with relatively low chromium, generally intended for strongly reducing acids such as hydrochloric acid. C-series alloys are nickel-chromium-molybdenum materials, sometimes with other additions, and are designed for a broader mix of oxidizing and reducing environments, including many chloride-containing conditions.
This is a useful starting point, not a substitute for application-specific material selection. Oxidizing contaminants, acid concentration, temperature, chloride level, flow conditions and fabrication history can all change which alloy is suitable.
Hastelloy X: A Different Kind of Challenge
In the 1950s, the development of Hastelloy X reflected a shift in industrial priorities. This nickel-chromium-molybdenum-iron alloy was designed for high-temperature strength and oxidation resistance. Unlike the B and C corrosion-resistant grades, Hastelloy X is best known for high-temperature service. It has been used in gas-turbine components, industrial furnaces and other equipment exposed to elevated temperatures.
C-276: A Milestone in Fabricable Corrosion Resistance
Hastelloy C-276 became a major milestone because it combined broad corrosion resistance with improved performance in welded fabrication. Commercially introduced in 1968, C-276’s low carbon and silicon content helped reduce welding-related corrosion concerns compared with earlier C alloys.
Under suitable service conditions and with qualified fabrication procedures, C-276 can often be used in the as-welded condition without mandatory post-weld solution heat treatment. Its balance of chromium and molybdenum supports resistance to many oxidizing and non-oxidizing acids, while also providing strong resistance to localized corrosion such as pitting and crevice attack in chloride-bearing environments.
These characteristics helped establish C-276 as a widely used material in chemical processing and other demanding industries. It is not immune to every corrosive environment, and no single alloy is suitable for every process. Its service life still depends on the actual chemistry, temperature, concentration and fabrication details.
A Growing Family of More Specialized Grades
As process requirements became more varied, new grades were developed to address specific combinations of corrosion and fabrication challenges. C-4, introduced in the 1970s, was designed to improve stability in welded and heat-affected areas. B-2 refined the nickel-molybdenum approach for reducing-acid service. C-22 broadened performance in oxidizing and chloride-containing environments, while G-30 was developed for demanding acid service, including wet-process phosphoric acid applications.
In the 1990s, B-3 improved structural stability over earlier B alloys, helping reduce concerns associated with fabrication and service. C-2000 balanced chromium, molybdenum and copper to address a wider mix of corrosive conditions. Later grades—including G-35, C-22HS and HYBRID-BC1—continued this trend toward application-specific solutions.
Choosing an Alloy Starts with the Service Environment
The history of Hastelloy is a history of solving real equipment problems. Each generation reflects a closer balance between corrosion resistance, weldability, fabrication and project cost. For material selection, the alloy name alone is not enough. Engineers should assess the process chemistry, acid concentration, temperature, oxidizing contaminants, chloride content, operating conditions and fabrication route before specifying a grade.
In 2024, Acerinox completed its acquisition of Haynes International. Haynes and VDM now form part of Acerinox’s High-Performance Alloys division.
Meet Shanghai Phoenix Alloy at ADIPEC 2026
As energy and process industries continue to face demanding materials challenges, Shanghai Phoenix Alloy Co., Ltd. will be at ADIPEC 2026, taking place 2–5 November at ADNEC Centre Abu Dhabi. Visit us at Stand 15453 to discuss nickel alloys and material requirements for your projects.