Alloy G-3 (UNS N06985) Overview and Applications

# Alloy G-3 (UNS N06985) Overview and Applications

## Introduction to Alloy G-3

Alloy G-3, also known by its UNS designation N06985, is a nickel-chromium-iron-molybdenum alloy with enhanced resistance to a wide range of corrosive environments. This alloy was specifically developed to offer superior performance in highly aggressive chemical processing applications where other materials might fail.

## Chemical Composition

The chemical composition of Alloy G-3 plays a crucial role in its exceptional corrosion resistance:

Nickel (Ni): 44% min

Chromium (Cr): 21-23.5%

Iron (Fe): 18-21%

Molybdenum (Mo): 6-8%

Copper (Cu): 1.5-2.5%

Tungsten (W): 1.5-2.5%

Carbon (C): 0.015% max

This balanced composition provides excellent resistance to both oxidizing and reducing acids, making it particularly suitable for harsh chemical environments.

## Key Properties

Corrosion Resistance

Alloy G-3 demonstrates outstanding resistance to sulfuric acid, phosphoric acid, and hydrochloric acid across a wide range of concentrations and temperatures. It also performs well in mixed acid environments containing oxidizing salts.

Mechanical Properties

The alloy maintains good mechanical strength at elevated temperatures and offers excellent fabricability, allowing for easy forming and welding operations.

Thermal Stability

Alloy G-3 retains its corrosion-resistant properties at high temperatures, making it suitable for applications involving heat exchangers and other high-temperature processing equipment.

## Common Applications

Chemical Processing Industry

Alloy G-3 is widely used in reactors, heat exchangers, and piping systems handling aggressive chemicals like sulfuric acid, phosphoric acid, and hydrochloric acid.

Pollution Control Equipment

The alloy’s resistance to flue gas condensates makes it ideal for scrubbers and other components in pollution control systems.

Oil and Gas Industry

Alloy G-3 finds applications in downhole components and piping systems where resistance to sour gas environments is required.

Pharmaceutical Manufacturing

The material’s purity and corrosion resistance make it suitable for pharmaceutical processing equipment.

## Fabrication and Welding

Alloy G-3 can be readily fabricated using standard techniques. For welding, matching filler metals are recommended, and proper heat treatment may be required for certain applications to maintain optimal corrosion resistance.

## Comparison with Similar Alloys

Compared to Alloy C-276, Alloy G-3 offers better resistance to sulfuric acid environments but may not perform as well in highly oxidizing conditions. The addition of tungsten in Alloy G-3 enhances its resistance to localized corrosion in chloride-containing environments.

## Conclusion

Alloy G-3 (UNS N06985) represents an excellent choice for applications requiring resistance to a wide spectrum of corrosive media, particularly in the chemical processing industry. Its balanced composition provides a cost-effective solution where more expensive alloys might otherwise be required, while still delivering reliable performance in demanding environments.