Acid-Resistant Steel
What is acid-resistant steel?
Acid-resistant steel is a special type of stainless steel designed for exceptional corrosion resistance in demanding environments. It contains at least 2% molybdenum (Mo), which enhances its ability to resist rust, pitting, and other forms of corrosion. Thanks to these properties, acid-resistant steel—often colloquially referred to as "acid-proof stainless"—is well suited for use in corrosive and solvent-rich environments.
Special Characteristics of Acid-Resistant Steel
- Molybdenum (Mo): The most important alloying element in acid-resistant steel is molybdenum, which provides improved corrosion resistance, especially in chloride and acidic environments. The molybdenum content is typically at least 2%, but in certain cases it can be 3% or more.
- Enhanced pitting resistance: Molybdenum reduces the steel's tendency to suffer from pitting corrosion, a common issue particularly in saltwater and other chloride-rich environments. This makes acid-resistant steel a highly reliable material for demanding conditions.
- Excellent general corrosion resistance: Acid-resistant steel protects against rust and other forms of corrosion in a wide variety of aggressive chemical environments, including acids and solvents.
Typical Acid-Resistant Steels
AISI 316:
- Description: The most common grade of acid-resistant steel, containing about 2–3% molybdenum, 16–18% chromium, and 10–14% nickel.
- Properties: Outstanding corrosion resistance, good weldability, and formability. Suitable for use in marine environments and the chemical industry.
- Applications: Tanks, pipes, valves, construction materials, and equipment for the food and beverage industry.
AISI 316L:
- Description: A low-carbon version of 316 steel, offering better weldability and minimizing disadvantages of higher carbon content, such as the risk of intergranular corrosion.
- Properties: Low carbon content improves weldability and reduces sensitivity to corrosion. Excellent corrosion resistance.
- Applications: Equipment requiring high weldability and corrosion resistance, such as medical devices, chemical processing equipment, and pharmaceutical tools.
AISI 904L:
- Description: A high-performance acid-resistant steel that has higher amounts of molybdenum and nickel, as well as copper.
- Properties: Extremely high corrosion resistance, especially in chlorides and acidic environments. Ideal for use in very demanding chemical settings.
- Applications: Sulfuric acid industry, seawater treatment equipment, oil and gas refining equipment.
Applications of Acid-Resistant Steel
Acid-resistant steel is the solution for many challenging and corrosion-prone environments:
- Marine and coastal environments: Saltwater is extremely corrosive, making acid-resistant steel an excellent material for a variety of marine equipment such as ships, harbor structures, and desalination units.
- Chemical industry: Many chemical processes that use strong acids and bases require acid-resistant steel for reactors, pipelines, and storage tanks.
- Food and pharmaceutical industries: In these fields, acid-resistant steel is the ideal choice for building tanks, piping, and processing equipment because it withstands various corrosive substances and cleaning chemicals exceptionally well.
- Oil and gas industry: Its excellent corrosion and oxidation resistance makes acid-resistant steel suitable for use in harsh and aggressive environments, such as offshore drilling and refineries.
Summary
Acid-resistant steel is a specialized stainless steel that contains at least 2% molybdenum and offers outstanding corrosion resistance in demanding environments. Its unique features, including enhanced pitting and general corrosion resistance, make it the ideal material for use in marine environments, the chemical industry, food and pharmaceutical industries, as well as the oil and gas industry. Typical acid-resistant steels include AISI 316, AISI 316L, and AISI 904L, each offering distinct advantages for long-term, reliable use in challenging conditions.
