PetroStreet

What are the major applied inspections and mitigations applied to keep Cl SCC under check?
Point me to some good literature over & above API 571 reference please.

I would first point towards the inspection applied on Cl-SCC.
Detection is notoriously difficult because cracks are often branched, fine, and filled with corrosion products.
Surface Techniques:
Liquid Penetrant Testing (PT): The "go-to" for surface-breaking cracks. Fluorescent PT is generally preferred over visible dye for higher sensitivity to fine branching.
Eddy Current Testing (ECT): Excellent for scanning large surfaces quickly. It is particularly effective for detecting cracks through thin coatings on heat exchangers tubes.

Volumetric Techniques:
Phased Array Ultrasonic Testing (PAUT): This in particular helps in characterizing crack depth and orientation. Specific "SCC-probes" are used to distinguish between pitting and the multi-branched nature of SCC.
Radiographic Testing (RT): Used primarily for detecting advanced cracking. Fine SCC can be missed by RT unless the crack is perfectly aligned with the beam.

Specialized Monitoring:
X-Ray Diffraction (XRD): Occasionally used to measure surface residual stresses to identify "hot spots" where cracking is likely to initiate.

Here, you need to recognize that mitigation follows the "SCC Triangle": Material, Stress, and Environment.
Material Selection (The "PREN" Approach)
Upgrade to Duplex SS: Moving from 316L to Duplex (e.g., 2205) significantly increases resistance due to the ferrite phase, which acts as a barrier to crack propagation.
High-Nickel Alloys: For extreme conditions (high T/high Cl), alloys like Incoloy 825 or Hastelloy C-276 are used as they are essentially immune.

Stress Management
Post-Weld Heat Treatment (PWHT): While not always standard for 300-series SS, a "solution anneal" or stabilization heat treatment can reduce residual stresses.
Shot/Laser Peening: Inducing compressive surface stresses to counteract the tensile stresses required for SCC initiation.
Design for Thermal Expansion: Ensuring piping layouts have sufficient flexibility to prevent high-stress points at elbows and tees.

Environmental & Barrier Controls
Thermal Spray Aluminum (TSA): Considered the "premium" mitigation for External Cl-SCC (under insulation). It acts as both a barrier and a sacrificial anode.
Insulation Management: Using "low-chloride" insulation (per ASTM C795) and ensuring robust weather-shielding to prevent water ingress.
Hydrotest Water Control: Using demineralized water (<50 ppm chlorides) and ensuring immediate drying/venting post-test to prevent "stagnant-pool" evaporation.

Thank you all.