NDE Coverage Gap When a Weld Is Coated Before Final Inspection

The three groove welds that were not MT-inspected are not released and must be treated as unverified. The inspection plan required MT before coating, and the specification does not permit inspection over coating. The fact that visual inspection passed does not substitute for MT, because MT detects surface and near-surface discontinuities that visual inspection cannot resolve, particularly at weld toes and in the HAZ.

MT over a cured zinc-rich primer is generally not acceptable. The primer is conductive and magnetic in some formulations, and it creates a standoff between the magnetizing field and the steel surface, which reduces sensitivity and can produce false indications or mask real ones. Even a thin primer can degrade the field and the particle mobility. The specification's prohibition reflects this. The coordinator should not accept an MT result obtained over the primer as evidence of compliance.

The correct status is: three groove welds are unverified and the skid cannot be released as compliant until they are inspected to the plan. The coordinator should notify the client and the shop, and treat the coating as an obstruction that must be removed locally for inspection.

The coordinator should present options with their schedule and technical consequences.

Option 1: Strip the primer locally and MT. Remove the coating from the three groove welds and a margin around them, perform MT, and re-coat the stripped areas. Risk: coating removal and re-coating take time and may not match the original finish; the re-coated area must be inspected for coating thickness and adhesion. This is the most compliant option and is likely achievable in five days if the areas are small.

Option 2: Strip, MT, and if indications are found, repair and re-inspect. This adds repair time and is the worst case for schedule. The coordinator should plan for it rather than assume the welds are clean.

Option 3: Request a client deviation to accept the three welds on the basis of visual inspection plus the three MT results. Risk: the client may refuse, and the coordinator would be accepting unverified welds. This should only be proposed if the client explicitly agrees and the technical basis is documented; it is not the coordinator's call.

Option 4: Ship with a hold and inspect at the destination. Risk: the client specification requires inspection before coating, and inspection after shipping may not be possible or may be rejected. This is generally not acceptable.

The coordinator should recommend Option 1, start the coating removal immediately, and notify the client of the schedule impact. Production pressure does not justify skipping the inspection.

The failure is a sequencing control gap: coating was applied before the inspection plan was complete, and there was no gate that prevented it.

Root cause: the inspection plan was not tied to a hold point in the production sequence. Visual inspection was completed, which may have created a false sense that inspection was done, and the coating crew had no instruction to verify MT completion before priming.

Corrective actions:

1. Add a hold point in the work order that blocks coating until all required NDE (visual, MT, and any other method) is signed off.
2. Require a pre-coating checklist signed by the NDE coordinator and the coating supervisor confirming each weld's inspection status.
3. Mark weld status physically (for example, a tag or color code) so the coating crew can see which welds are released.
4. Include the inspection sequence in the production schedule so coating is planned after NDE, not before.
5. Brief both the fabrication and coating crews on the specification requirement and the consequence of inspection over coating.

Verification: the coordinator should audit the next skid to confirm the hold point works, and close the corrective action only after a clean audit. The goal is to make the correct sequence the default, not to rely on memory under schedule pressure.