Amine cracking is a serious failure mechanism in carbon and low-alloy steels, particularly in the heat-affected zone (HAZ) of welds. Here's what matters for inspection and prevention:

The mechanism: Amine-based treating chemicals (used in refining and petrochemical processes) can cause stress-corrosion cracking in susceptible microstructures, especially in hardened HAZ regions where residual tensile stresses are high. The cracking is typically intergranular and delayed — it may appear hours or days after welding.

Prevention is key:

• Material selection: use steels with lower carbon equivalence (CE) to reduce HAZ hardness
• Preheat and interpass temperature control to slow cooling and reduce hardness
• Post-weld heat treatment (PWHT) to relieve residual stresses — this is the most effective control
• Hydrogen control: keep diffusible hydrogen low by using low-hydrogen welding processes and consumables

Inspection:

• Ultrasonic testing (UT) and radiography (RT) can detect cracks, but amine cracking is often tight and subsurface — detection is challenging
• Phased array UT (PAUT) offers better sensitivity to tight, near-vertical cracks in the HAZ
• Surface methods (PT, MT) help find surface-breaking indications
• The governing code — ASME B31.3 for process piping, API 579 for fitness-for-service, or your project specification — defines acceptance criteria and inspection requirements

The specific inspection technique, acceptance limits and repair decisions must follow your applicable code, written procedure and a Level III or authorised inspector. If amine cracking is suspected in service, consult the relevant fitness-for-service standard and your materials engineer.