Alloy C22

Titanium

Nickel

Overview

Grades & Materials

Pure Nickel

Nickel–Chromium Alloys

Nickel–Molybdenum Alloys

Nickel–Chromium–Molybdenum Alloys

Alloy 625

Alloy C276

Alloy C22

Nickel–Iron Alloys

Applications

Products

Standards & Quality

Technical Knowledge

Selection Guide

Stainless

Carbon

Alloy

Copper, Brass and Bronze

Alloy C22

Alloy C22 is a nickel–chromium–molybdenum (Ni–Cr–Mo) alloy engineered to deliver the broadest corrosion resistance within the Ni–Cr–Mo family.
It is particularly effective against pitting, crevice corrosion, and stress corrosion cracking across highly oxidizing, reducing, and chloride-rich environments, making it a preferred choice for critical chemical processing and heat exchanger service.

Within the Ni–Cr–Mo system, Alloy C22 is positioned as the maximum corrosion-margin grade.

Chemical & Metallurgical Characteristics

Alloy C22 employs a high chromium + high molybdenum design in a nickel matrix to suppress multiple corrosion mechanisms simultaneously.

Key Metallurgical Features

  • High Ni for matrix stability and toughness

  • Elevated Cr for oxidation resistance and SCC mitigation

  • Elevated Mo for superior pitting and crevice corrosion resistance

  • Low Fe for improved corrosion reliability

  • Stable FCC microstructure with excellent ductility

This balance provides exceptional tolerance to process variability.

Corrosion Resistance Performance

Alloy C22 is optimized for severe and unpredictable corrosion exposure.

Excellent Resistance In:

  • Strong oxidizing and reducing acids

  • Chloride-containing environments

  • Pitting and crevice corrosion

  • Stress corrosion cracking

  • Wet chlorine, hypochlorites, and ferric solutions

Compared with Other Ni–Cr–Mo Grades:

  • Higher pitting/crevice resistance than Alloy C276

  • Broader oxidation tolerance than Alloy 625

  • Best choice where corrosion mechanisms overlap

Mechanical Properties (Typical)

Alloy C22 provides:

  • Moderate tensile and yield strength

  • Excellent ductility and toughness

  • Stable properties across ambient to elevated temperatures

Mechanical strength is adequate for pressure service, while corrosion resistance remains the primary design driver.

Typical Applications

Alloy C22 is selected for the most demanding corrosion-critical equipment.

Common Applications Include:

  • Chemical reactors and vessels

  • Heat exchangers handling mixed acids

  • Flue gas desulfurization (FGD) systems

  • Pulp & paper bleaching equipment

  • Waste treatment and pollution control systems

It is frequently specified when long service life and maximum safety margin are required.

Product Forms Available

Alloy C22 is commonly supplied in:

  • Seamless tubes

  • Pipes

  • Plates and sheets

  • Bars and rods

  • Forgings, fittings, and tube sheets

For thermal and chemical equipment, seamless Alloy C22 tubes are preferred for:

  • Uniform wall thickness

  • Reliable pressure integrity

  • Consistent corrosion performance

Manufacturing & Fabrication

Alloy C22 can be fabricated using standard nickel-alloy practices:

  • Hot and cold working

  • Solution annealing

  • Conventional welding with clean procedures

Strict cleanliness and heat-treatment control are recommended to preserve maximum corrosion resistance.

Standards & Specifications

Alloy C22 products are commonly supplied to:

  • ASTM material standards

  • ASME pressure equipment codes

  • Project-specific chemical service requirements

Typical Inspection & Testing:

  • Chemical composition analysis

  • Mechanical testing

  • Dimensional inspection

  • Eddy current or ultrasonic testing (for tubes)

  • PMI verification

Complete Mill Test Certificates (MTC) and traceability are standard.

Alloy C22 vs Alloy C276 / Alloy 625 (Concept)

  • Alloy C22

    • Broadest corrosion resistance

    • Best pitting/crevice performance

    • Preferred for mixed, high-risk environments

  • Alloy C276

    • Excellent general corrosion resistance

    • Slightly lower pitting resistance than C22

    • Cost-effective for many severe chemical services

  • Alloy 625

    • Better strength–corrosion balance

    • Preferred where pressure strength is critical

Selection depends on whether maximum corrosion margin or mechanical strength/cost balance is the priority.

Summary

Alloy C22 is positioned within Nickel → Grades & Materials → Nickel–Chromium–Molybdenum Alloys and is selected for the most aggressive mixed corrosive environments.

Explore next:

  • Grades: Alloy 625 · Alloy C276

  • Applications: Heat Exchangers · Chemical Processing · Marine & Offshore

  • Guide: Nickel Selection Guide