Alloy 625

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

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Copper, Brass and Bronze

Alloy 625

Alloy 625 is a nickel–chromium–molybdenum (Ni–Cr–Mo) alloy known for its exceptional resistance to pitting, crevice corrosion, and stress corrosion cracking, combined with high strength over a wide temperature range.
It is one of the most widely specified Ni–Cr–Mo grades for heat exchangers, chemical processing equipment, marine systems, and pressure applications where mixed corrosive environments exist.

Within the nickel material system, Alloy 625 is often treated as a default “safe choice” when corrosion mechanisms are complex or difficult to control.

Chemical & Metallurgical Characteristics

Alloy 625 derives its performance from a balanced Ni–Cr–Mo chemistry, with strengthening primarily from solid-solution effects.

Key Metallurgical Features

  • High nickel content for matrix stability and toughness

  • Chromium for oxidation resistance and SCC resistance

  • Molybdenum for pitting and crevice corrosion resistance

  • Stable face-centered cubic (FCC) structure

  • No reliance on precipitation hardening for corrosion performance

This design provides consistent properties in both annealed and service conditions.

Corrosion Resistance Performance

Alloy 625 is engineered for broad-spectrum corrosion resistance.

Excellent Resistance In:

  • Chloride-containing environments

  • Pitting and crevice corrosion

  • Stress corrosion cracking

  • Mixed oxidizing and reducing media

  • Seawater and marine atmospheres

Limitations:

  • Not optimized for pure strong reducing acids (Ni–Mo alloys may perform better)

  • May be over-specified for simple, well-controlled environments

Overall, Alloy 625 performs reliably in real-world industrial conditions, where chemistry may fluctuate.

Mechanical Properties (Typical)

Alloy 625 offers:

  • High tensile and yield strength

  • Excellent toughness and ductility

  • Good fatigue and thermal stability

  • Strength retention from cryogenic to elevated temperatures

These properties allow Alloy 625 to be used in pressure-containing and cyclic-load applications in addition to corrosion-critical service.

Typical Applications

Alloy 625 is widely used across industries requiring both corrosion resistance and mechanical reliability.

Common Applications Include:

  • Heat exchanger and condenser tubing

  • Chemical and petrochemical reactors

  • Offshore and marine piping systems

  • Desalination and seawater handling equipment

  • Pressure vessels and high-integrity components

It is frequently selected when failure risk must be minimized.

Product Forms Available

Alloy 625 is commonly supplied in:

  • Seamless tubes

  • Pipes

  • Plates and sheets

  • Bars and rods

  • Forgings, fittings, and tube sheets

For heat transfer and pressure equipment, seamless Alloy 625 tubes are preferred due to:

  • Uniform wall thickness

  • High pressure capability

  • Consistent corrosion performance

Manufacturing & Fabrication

Alloy 625 is well-suited to fabrication using standard practices:

  • Hot and cold working

  • Solution annealing

  • Conventional welding methods

The alloy exhibits good weldability and formability, making it suitable for complex assemblies without significant loss of properties.

Standards & Specifications

Alloy 625 products are commonly supplied to:

  • ASTM material standards

  • ASME pressure equipment codes

  • Project-specific technical specifications

Typical Inspection & Testing:

  • Chemical composition analysis

  • Mechanical testing

  • Dimensional inspection

  • Eddy current or ultrasonic testing (for tubes)

  • PMI verification

Full Mill Test Certificates (MTC) and traceability are typically provided.

Alloy 625 vs Other Ni–Cr–Mo Grades (Concept)

  • Alloy 625

    • Balanced corrosion resistance and strength

    • Excellent fabricability

    • Widely used across industries

  • Alloy C276 / C22

    • Higher resistance to extremely aggressive chemical environments

    • Lower mechanical strength emphasis

    • Preferred for severe acid service

Grade selection depends on corrosion severity, mechanical requirements, and fabrication needs.

When to Choose Alloy 625

Alloy 625 is recommended when:

  • Multiple corrosion mechanisms may occur

  • Chlorides and acids are both present

  • Mechanical strength is required alongside corrosion resistance

  • Long service life and safety margin are critical

It may be over-specified when:

  • The environment is simple and well-controlled

  • Corrosion mechanisms are clearly limited

Summary

Alloy 625 is positioned within Nickel → Grades & Materials → Nickel–Chromium–Molybdenum Alloys and is selected for mixed corrosive environments requiring both corrosion resistance and mechanical strength.

Explore next:

  • Grades: Alloy C276 · Alloy C22

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

  • Guide: Nickel Selection Guide