Hydrogen Damage Behavior of X80 Pipeline Steel Under AC Interference

Area of Science:

• Materials Science
• Corrosion Engineering
• Electrochemistry

Background:

• X80 pipeline steel is critical for oil and gas transport.
• Hydrogen embrittlement poses a significant risk to pipeline integrity.
• Understanding hydrogen damage mechanisms is vital for safety.

Purpose of the Study:

• To compare the electrochemical responses and hydrogen-induced cracking of X80 base metal and welded joints.
• To investigate the effects of alternating current (AC) and direct current (DC) hydrogen charging.
• To evaluate the influence of current density and polarization on hydrogen permeation and embrittlement.

Main Methods:

• Hydrogen permeation experiments were conducted.
• Slow strain rate tensile tests were performed.
• Electrochemical responses under AC and DC hydrogen charging were analyzed.

Main Results:

• AC hydrogen charging at 20 mA/cm² resulted in the highest hydrogen permeation flux.
• Welded joints exhibited lower overall hydrogen permeation parameters than the base material.
• Direct current (DC) charging led to more significant mechanical property degradation and higher stress corrosion cracking sensitivity compared to AC charging.

Conclusions:

• High-frequency polarization generally promotes hydrogen permeation, but anodic products can hinder hydrogen entry at high current densities.
• Alternating current (AC) hydrogen charging demonstrated lower hydrogen embrittlement sensitivity due to alternating cathodic and anodic effects.
• Direct current (DC) hydrogen charging poses a greater risk to X80 pipeline steel integrity due to more severe mechanical property decline and increased susceptibility to stress corrosion cracking.