What matters most
A coating assessment should document where and how the system lost adhesion, continuity, thickness, or barrier performance, then relate that pattern to substrate preparation, edges and welds, cure, environment, mechanical damage, immersion, and corrosion beneath or at defects. Rust alone does not identify the coating failure mode.
Key takeaways
- Map defect type and distribution before surface preparation or repair changes the evidence.
- Inspect edges, welds, crevices, penetrations, supports, splash zones, soil lines, and areas that trap water.
- Distinguish adhesion, cohesion, underfilm corrosion, blistering, cracking, impact, abrasion, and chemical degradation.
- Use coating measurements and samples only when they answer the maintenance or failure question.
The coating changes the exposure
A protective coating separates the substrate from the electrolyte and can greatly reduce the area available for corrosion. Performance depends on continuity, adhesion, thickness, permeability, compatibility, cure, and resistance to the actual environment.
Small defects may become important when the surrounding system concentrates current or moisture at the exposed metal. Coating condition therefore changes both the chemistry and geometry of the corrosion cell.
Map distress before repair
Record defect type, size, density, orientation, elevation, immersion zone, soil line, splash exposure, color, deposits, substrate condition, and proximity to welds, edges, penetrations, supports, and prior repairs.
Photographs and a consistent rating or map allow the owner to compare areas and plan repairs. A few closeups without location context cannot establish the extent.
Distinguish coating failure modes
Loss of adhesion, cohesive splitting, blistering, cracking, checking, pinholes, holidays, underfilm corrosion, impact damage, abrasion, ultraviolet degradation, chemical attack, and osmotic effects have different implications.
A coating can be intact but unsuitable for the environment, or chemically compatible but poorly prepared or cured. The evaluation should not attribute every defect to age.
Pay attention to crevices, edges, and water traps
Sharp edges often receive less effective dry-film thickness, while incomplete weld geometry, lap joints, penetrations, bolts, and supports can trap electrolyte. Ponded water, splash zones, irrigation, leaks, and poor drainage extend time of wetness.
These locations deserve focused inspection because they can create localized conditions more aggressive than the surrounding surface.
Select measurements for the maintenance decision
Potential work includes dry-film thickness, adhesion testing, holiday detection, soluble-salt or contamination testing, material identification, microscopy, and targeted coating samples. Destructive tests should be placed and repaired intentionally.
The required standard, acceptance criterion, and sampling frequency should come from the coating system, specification, owner program, and question—not from a generic checklist.
Translate findings into a repair scope
The report can rank areas, identify preparation and access needs, distinguish spot repair from broader rehabilitation, and flag conditions that must be corrected before recoating. It should also identify uncertainty where inaccessible areas were not observed.
Calicore provides coating condition assessment and rehabilitation support for tanks, piping, facilities, and infrastructure. Specialized coating inspection or laboratory analysis can be coordinated as required.
This article is general educational information, not a project-specific engineering conclusion. Site conditions, service environment, material, geometry, governing documents, and available evidence must be evaluated for the actual project. Calicore Engineering does not currently provide cathodic protection system design.
Frequently asked
Questions about this topic
Does visible rust prove the coating product was defective?+
No. Product compatibility, surface preparation, application, cure, thickness, geometry, mechanical damage, environment, and maintenance all require evaluation.
Can a coating assessment be performed while an asset remains in service?+
Often yes for accessible surfaces, but service conditions and access limit what can be safely observed or tested. Immersed or internal areas may require an outage.
Does coating assessment include cathodic-protection design?+
No. Calicore can evaluate coating condition and note coordination needs; CP system design is outside the current service offering.