Map the emergence points

Compare a pinpoint stain, a line following a scratch and a broad stain below an attachment. Repeated points within one area can justify a different investigation from a single runoff trail. Existing close images should show coating edges, raised areas and nearby joints without concealing the surface beneath annotations. A change in lighting can hide small discontinuities, so absence of a visible pinhole is not proof that none exists.

Separate film and substrate questions

A coating review asks about adhesion, continuity and the condition of individual layers. A substrate review asks about corrosion and remaining material. Both may be needed, but one does not replace the other. Qualified examination can establish whether coating removal at selected locations is warranted; uncontrolled scraping or sanding may destroy useful boundary evidence. The original substrate preparation and coating history can help distinguish local damage from a system-wide problem.

If staining follows an old repair perimeter, ask whether the repair boundary or underlying preparation deserves examination. If it begins above that perimeter, investigate runoff first. Choosing between those paths can prevent unnecessary removal of an otherwise unrelated area of coating.

Avoid a cosmetic-only closure

Touch-up should follow a defined understanding of the affected area and a compatible repair specification. Otherwise new paint may temporarily hide continuing rust discharge. Ask the reviewer whether the source has been identified and whether hidden surrounding deterioration has been bounded. The decision must specify what was established about both protection and component condition. No coating system, expected lifetime or permitted corrosion extent is asserted for MARSTON by this symptom.