Hydrogen Blistering

Hydrogen blistering is a type of corrosion that occurs when hydrogen atoms penetrate the surface of a metal and accumulate within the metal structure. This can occur in environments with hydrogen sulfide (H2S), such as in the oil and gas industry.

When hydrogen atoms accumulate within the metal, they can form internal blisters that weaken the metal, eventually leading to cracking and failure. Unfortunately, these blisters can be challenging to detect, as they are internal and may not be visible on the surface of the metal.

To prevent hydrogen blistering, it is crucial to control the presence of H2S in the environment and select materials resistant to this type of corrosion. Protective coatings and cathodic protection can also be used to prevent hydrogen blistering.

If hydrogen blistering is suspected, it is essential to conduct inspections and testing to determine the damage's extent and take appropriate corrective actions to prevent further deterioration of the metal.

Factors that cause hydrogen blistering

The factors that contribute to hydrogen blistering can vary but generally include the following:

• Presence of hydrogen: This is the most critical factor in hydrogen blistering. The presence of hydrogen, either in the form of atomic hydrogen or molecular hydrogen, is necessary for blistering to occur.
• Material properties: Some materials are more susceptible to hydrogen blistering than others. Materials with high hydrogen solubility or high hydrogen permeability will likely experience hydrogen blistering.
• Environmental conditions: Certain environmental conditions, such as high temperature and pressure, can promote the formation of hydrogen blisters.
• Hydrogen concentration: Higher concentrations of hydrogen can accelerate the formation of hydrogen blisters.
• Mechanical stress: Mechanical stress can increase the likelihood of hydrogen blistering by creating sites where hydrogen can accumulate and form blisters.
• Surface condition: The condition of the metal surface can also influence the likelihood of hydrogen blistering. Rough surfaces and surfaces with defects can provide sites for hydrogen accumulation and blister formation.
• Time: The longer a metal is exposed to hydrogen, the more likely it is to experience hydrogen blistering.

It is essential to understand and control these factors to prevent hydrogen blistering from occurring.

Preventative measures

Several preventative measures can be taken to reduce the risk of hydrogen blistering:

• Control the environment: Control the environment in which the metal is exposed to hydrogen. This can be done by minimizing the presence of hydrogen or eliminating it. This can be achieved through process design, such as using hydrogen scavengers or inhibitors, or through engineering controls, such as ventilation or the use of protective barriers.
• Select appropriate materials: Select materials that are resistant to hydrogen blistering. This can be done by choosing materials with low hydrogen solubility or permeability. Alternatively, coatings or surface treatments can be applied to increase resistance to hydrogen.
• Monitor the environment: Monitor the environment for hydrogen and other corrosive gases. This can be done through regular testing and inspection.
• Control mechanical stress: Control mechanical stress in the metal. This can be done by avoiding excessive loading, reducing residual stresses, and controlling the temperature.
• Maintain good surface condition: Maintain good surface condition by regularly inspecting and repairing defects. This can help to prevent the accumulation of hydrogen and the formation of blisters.
• Apply cathodic protection: Cathodic protection is a technique used to prevent corrosion by applying a protective current to the metal surface. This can be an effective way to avoid hydrogen blistering in specific environments.

Conduct regular inspections: Conduct regular inspections and testing to identify any signs of hydrogen blistering or other types of corrosion. This can help to detect and address issues before they become more serious.

Inspection for hydrogen blistering

There are several methods for inspecting for hydrogen blistering:

• Visual Inspection: Visual inspection involves examining the surface of the metal for signs of blistering. Hydrogen blisters may appear as raised, rounded areas on the surface of the metal. However, since hydrogen blisters are often internal and not visible on the surface, this method may not be sufficient.
• Ultrasonic Testing: Ultrasonic testing uses sound waves to detect internal flaws in the metal, including hydrogen blisters. The ultrasonic waves are sent through the metal, and the reflected waves are measured to identify any abnormalities in the metal structure.
• Radiographic Testing: Radiographic testing uses X-rays or gamma rays to create an image of the metal's internal structure. Hydrogen blisters may appear as dark areas in the image, indicating a lack of material density.
• Magnetic Particle Testing: Magnetic particle testing detects surface and near-surface defects in ferromagnetic materials. It involves applying a magnetic field to the metal and then applying magnetic particles to the surface. Any defects in the metal will disrupt the magnetic field, causing the particles to cluster around the defect and indicating the presence of a blister.
• Eddy Current Testing: Eddy current testing uses electromagnetic induction to detect surface and near-surface defects in the metal. An electrical current is induced in the metal, which creates a magnetic field. Any defects in the metal will cause a change in the magnetic field, which can be detected and used to identify the location and extent of any hydrogen blisters.

The appropriate method of inspection will depend on the type of metal, the location of the suspected blistering, and the specific inspection requirements. A combination of techniques may be used to ensure that all possible defects are detected.

The specification is used for hydrogen blistering prevention and inspection.

API (American Petroleum Institute) has no specific specification dedicated to hydrogen blistering. However, API provides several specifications and recommended practices that address the prevention and detection of hydrogen blistering, including:

• API RP 571: Damage Mechanisms Affecting Fixed Equipment in the Refining Industry - This recommended practice covers various damage mechanisms affecting fixed equipment in the refining industry, including hydrogen blistering.
• API RP 580: Risk-Based Inspection - This recommended practice provides guidelines for developing and implementing risk-based inspection (RBI) programs for fixed equipment in the refining and petrochemical industries. Hydrogen blistering is one of the damage mechanisms that can be addressed in an RBI program.
• API RP 939-C: Guidelines for Avoiding Sulfidation (Sulfidic) Corrosion Failures in Oil Refineries - This recommended practice provides guidelines for avoiding sulfidation corrosion failures in oil refineries, which can lead to hydrogen blistering.
• API 510: Pressure Vessel Inspection Code - This standard provides inspection and repair practices for pressure vessels in the refining and petrochemical industries, including guidelines for inspecting hydrogen blistering.
• API 653: Tank Inspection, Repair, Alteration, and Reconstruction - This standard provides inspection and repair practices for aboveground storage tanks, including guidelines for inspecting hydrogen blistering.

These API specifications and recommended practices guide preventing, detecting, and addressing hydrogen blistering in the oil and gas industry.

NACE International, a professional association focused on corrosion prevention and control, provides several specifications and recommended practices related to hydrogen blistering, including:

• NACE MR0175/ISO 15156: Petroleum, petrochemical, and natural gas industries - Materials for use in H2S-containing environments in oil and gas production - This standard provides requirements and recommendations for materials used in environments containing H2S, including guidelines for avoiding hydrogen blistering.
• NACE SP0490: Wet H2S Cracking in Oil and Gas Production - This standard provides guidelines for preventing and detecting wet H2S cracking, including hydrogen blistering, in oil and gas production.
• NACE SP0169: Control of External Corrosion on Underground or Submerged Metallic Piping Systems - This standard provides guidelines for controlling external corrosion on underground or submerged metallic piping systems, including preventing hydrogen blistering.
• NACE SP0102: Inline Inspection of Pipelines - This standard provides guidelines for conducting an inline inspection of pipelines, including methods for detecting hydrogen blistering.
• NACE SP0170: Mitigation of Alternating Current and Lightning Effects on Metallic Structures and Corrosion Control Systems - This standard provides guidelines for mitigating alternating current and lightning effects on metallic structures and corrosion control systems, which can contribute to hydrogen blistering.

These NACE specifications and recommended practices guide preventing, detecting, and addressing hydrogen blistering in the oil and gas industry and other industries where H2S corrosion can occur.