Hastelloy C22 Hex Head Bolt Applications

Fasteners fail where corrosion concentrates: in pits, in crevices and under tensile stress. Hastelloy C22 hex head bolts — a nickel-chromium-molybdenum alloy with tungsten, iron, niobium and tantalum — resist pitting, crevice corrosion and stress corrosion cracking across marine, chemical, offshore and power service, while the sealing interface still depends on the right gasket materials.

Alloy Profile and Properties

Hastelloy C22 is primarily nickel, chromium and molybdenum, with small amounts of tungsten and iron. It resists both oxidizing and reducing environments, and the niobium and tantalum present improve crevice corrosion resistance.

• Composition — nickel, chromium and molybdenum base with tungsten and iron, plus niobium and tantalum.
• Mechanical — high tensile strength for demanding bolted joints, with good ductility across high and low temperatures.
• Corrosion media — chlorides, sulfuric acid, nitric acid, phosphoric acid and hydrochloric acid.
• Failure modes resisted — pitting, crevice corrosion and stress corrosion cracking.

That combination makes hex head bolts from this alloy the default where ordinary stainless steels pit, crack or seize.

Pitting, Crevice and Stress Corrosion Cracking

Hastelloy C22 answers all three damage mechanisms with one alloy.

• Pitting — localized attack that breaks the passive film and drills small holes; C22 forms a stable film that stops pit initiation.
• Crevice corrosion — confined spaces such as pipe flanges and gasket faces trap a stagnant electrolyte; niobium and tantalum additions slow it down.
• Stress corrosion cracking — tensile stress plus a corrosive medium; the alloy's composition and microstructure resist it even under significant stress.

Hex Head Bolt Applications by Industry

Six sectors account for most of the demand.

• Marine — shipbuilding, offshore platforms and seawater filtration systems exposed to saltwater and humidity.
• Chemical processing — reactors, heat exchangers and storage tanks handling acids, alkalis and halogens.
• Offshore oil and gas — wellhead equipment, subsea pipelines and drilling platforms facing hydrogen sulfide and chlorides.
• Desalination — reverse osmosis systems, heat exchangers and saltwater pumps.
• Power generation — fossil and nuclear plants: gas turbines, steam generators and heat exchangers.
• Aerospace — jet engines and other components under high temperature, pressure and corrosive atmospheres.

Field experience backs the specification: offshore wind turbines bolt tower, rotor blades and nacelle with this alloy, chemical reactors gain leak-free life, and nuclear plants use it for reactor internals, steam generators and control rod drive mechanisms.

Frequently Asked Questions

What is Hastelloy C22 made of?

A nickel-chromium-molybdenum alloy with small amounts of tungsten and iron, plus niobium and tantalum that improve crevice corrosion resistance.

Which corrosive media does it resist?

Chlorides, sulfuric acid, nitric acid, phosphoric acid and hydrochloric acid, in both oxidizing and reducing environments.

Why do crevices matter for bolts?

Crevice corrosion starts in confined spaces like flange and gasket faces, where trapped electrolyte corrodes the metal faster than open surfaces.

Where are Hastelloy C22 hex head bolts used?

Marine, chemical processing, offshore oil and gas, desalination, power generation and aerospace — from seawater pumps to jet engines.

Do they resist stress corrosion cracking?

Yes — the composition and microstructure resist cracking under significant tensile stress, which is why they are specified in environments prone to it.