ASTM A193 B8M Stainless Steel — Specs, Uses & Applications

When projects demand maximum corrosion resistance, especially in marine, coastal, or chemical-rich environments, not every fastener can perform. That’s why ASTM A193 Grade B8M has become one of the most specified stainless steel fastener standards in industry.

Derived from 316 stainless steel, B8M fasteners include molybdenum for superior protection against chlorides, pitting, and aggressive chemicals. From offshore oil rigs and desalination plants to pharmaceutical production facilities, A193 B8M delivers durability where failure isn’t an option.

This article explores the B8M specification—its properties, classes, applications, and why sourcing from a trusted supplier like California Fastener is essential for success.

What Is ASTM A193 B8M?

ASTM A193 B8M defines fasteners manufactured from 316 stainless steel, an austenitic alloy with 2–3% molybdenum. That small addition provides a major performance boost, giving B8M fasteners far greater resistance to chloride stress cracking and chemical attack compared to 304-based stainless (B8).

Key characteristics:

• Exceptional corrosion resistance, especially in chloride-heavy or marine environments.

• Strength at elevated temperatures, suitable for industrial service.

• Versatility in form: studs, threaded rods, and heavy-duty fasteners.

• Durability in seawater, brine, and harsh chemical environments.

This makes B8M the go-to specification for environments that would quickly compromise lesser grades.

Classes: 1 vs. 2

B8M fasteners are produced in two classes, tailored to different needs:

• Class 1: Carbide solution treated for maximum corrosion resistance. Best for marine, offshore, food, and pharmaceutical service, where exposure to salts or cleaning chemicals is constant.

• Class 2: Strain-hardened for greater tensile strength while retaining corrosion resistance. Common in chemical plants and heavy industrial applications where added load capacity is required.

Selecting the right class ensures that the fastener system aligns with both environmental and mechanical requirements.

Properties & Heat Treatment

• Tensile strength: 75–125 ksi depending on class.

• Yield strength: 30–95 ksi.

• Non-magnetic in the annealed state; strain-hardened material may show slight magnetism.

• Carbide solution treatment prevents intergranular corrosion.

• Molybdenum advantage: Provides resistance to chloride-induced pitting, making B8M ideal for coastal and chemical facilities.

By balancing strength with unmatched corrosion resistance, B8M ensures fasteners provide decades of reliable service.

Compatible Nuts: ASTM A194

Fasteners made to A193 B8M are paired with ASTM A194 Grade 8M nuts, also manufactured from 316 stainless steel. This ensures:

• Corrosion compatibility between nut and fastener.

• Even load distribution under stress.

• Smooth installation, reducing galling risk.

For spec compliance and long-term reliability, using Grade 8M nuts with B8M fasteners is essential.

Applications of ASTM A193 B8M

The durability of A193 B8M makes it essential in industries where fasteners face salt, chemicals, or repeated cleaning:

• Marine and offshore structures: oil rigs, dock equipment, and seawater piping.

• Chemical plants: joints and flanges exposed to aggressive chemical solutions.

• Desalination systems: high-chloride water treatment equipment.

• Food & beverage plants: sanitary fasteners resistant to repeated washdowns.

• Pharmaceutical facilities: hygienic fasteners with long-term reliability.

In these sectors, downtime caused by fastener corrosion is unacceptable—B8M ensures equipment integrity.

California Fastener’s Offering

At California Fastener, we stock and supply ASTM A193 B8M fasteners in a variety of forms and classes, with:

• Deep inventory in multiple diameters and lengths.

• Both Class 1 and Class 2 available with full certifications.

• Matching A194 Grade 8M nuts for compliant assemblies.

• Pre-kitted packages to streamline installation and reduce labor hours.

• Reliable fulfillment timelines to keep critical projects on track.

We support industries where uptime is essential and fastener performance cannot be compromised.

FAQs About ASTM A193 B8M

Q: What makes A193 B8M different from A193 B8?
A: B8M is made from 316 stainless steel, while B8 is 304. The molybdenum in B8M gives it superior chloride and chemical resistance.

Q: Is B8M magnetic?
A: No, B8M is non-magnetic when annealed, though strain-hardening can introduce slight magnetism.

Q: What nuts should be paired with B8M fasteners?
A: Always use ASTM A194 Grade 8M nuts for compatibility and compliance.

Q: Where is B8M most commonly used?
A: Marine, desalination, chemical processing, food & beverage, and pharmaceutical facilities.

Q: Can B8M fasteners be coated?
A: Yes—though often unnecessary, coatings or passivation can extend service life in harsh conditions.

Standing Strong in the Harshest Environments

ASTM A193 B8M is the specification of choice when corrosion resistance and reliability are mission-critical. From offshore platforms to chemical plants, it ensures fasteners perform where standard stainless steels would fail.

At California Fastener, we deliver spec-compliant, certified A193 B8M fasteners, ready to ship and backed by dependable supply.

Contact us today to source ASTM A193 B8M studs, rods, and fasteners—engineered for the world’s most demanding environments.