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Coating_Defects_Webinar JLA.pptx
- 2. Coating Defects andFailures Presented by: Sarah Olthof
- 3. Topics • Consequences ofcoating failure • Role of coatings inspector in failure avoidance • Common coating failures and defects
- 4. Scope • This webinardescribes the consequences of coating failures, field and laboratory investigative processes undertaken to diagnose coating failures, and reviews common coating defects and failures.
- 5. Learning Outcomes • Atthe end of this unit, the student will be able to: – Recognize the consequences of coating failures – Describe the coating inspector’s role in preventing failures – Identify common coating failures and defects seen in the field
- 6. Protective Coatings • Principalmaterial used for corrosion protection • All coatings will breakdown over time • Service life can be extended by performing maintenance painting once deterioration is identified
- 7. Premature Coating Failure •Failures that occur before the anticipated service life ends can be caused by: – Improper surface preparation – Improper coating application procedures – Improper coating system selection – Improper formulation – Poor quality raw materials
- 8. Once Premature FailureOccurs… • The investigation begins……. – What was the cause of the premature coating failure? – What party was responsible for the failure? – What level of repair is required to ensure corrosion protection and integrity of the structure is acceptable?
- 9. Consequences of CoatingFailures • Financial impacts • Litigation • Substrate repair or replacement • Costly rework and downtime
- 10. Substrate Repair orReplacement • When a failure occurs, the substrate is exposed to the environment until the defect is detected • Unprotected substrate is susceptible to corrosion and possible section loss • Integrity of structure could be compromised if coating failure is not detected for an extended period of time • Cost to repair substrate adds to the cost of the coating failure
- 11. Rework and Downtime •Remobilization, surface preparation, coating application, and inspection of the repair or rework can be time consuming and costly. • Hard to determine extent of rework needed. – Does the failure indicate total removal? – Can we get away with a spot repair?
- 12. Role of aCoating Inspector • The inspector can play a key role in helping to prevent premature coating failure. • Qualified inspection personnel can significantly reduce the opportunity for failure
- 13. Identification of a Non-Conformance •The inspector: – Identifies deficiencies as they arise – Will work with contractor for reaction plan once non-conformance is identified
- 14. Common Coating Defectsand Failures
- 15. Delamination • Results fromloss of adhesion between the substrate and coating OR between coats.
- 16. Delamination • Common Causes •Poor surface preparation • Intercoat cleanliness • Exceeding overcoating times • Incompatibility of topcoat and primer • Remediation • Area with poor adhesion must be completely removed and the cause should be evaluated before recoating.
- 17. Blistering • Coating liftingfrom the underlying substrate
- 18. Blistering • Common Causes •Contamination on the substrate • Oils and greases • Soluble Salts (osmotic blistering) • Solvent entrapment • Remediation • Ensure correct surface preparation and application • Soluble salt testing
- 19. Blush • Haze oroily residue on the surface of a coating
- 20. Blush • Common Causes •High humidity or cold temperatures during application • Curing stages of an epoxy • Intensified by cool temperatures and increased coating thickness • Remediation • Blush will effect adhesion of topcoat • If blush is detected (not easy to detect) it is best practice to consult with product manufacturer on removal tactics
- 21. Sags/Runs • Downward movement ofpaint soon after application on vertical surfaces
- 22. Sags/Runs • Common Causes •Over application • Excessive thinning • Poor workmanship • Remediation • While wet, sags/runs should be smoothed with a paint brush • If dry, abrade, clean, and apply spot coat
- 23. Orange Peel • Pockedappearance; surface of paint film resembles the skin of an orange
- 24. Orange Peel • CommonCauses • Poor application techniques • Incorrect solvent blend • Remediation • Abrade • Clean • Recoat
- 25. Pinholes • Formation oftiny holes in wet paint film during application and drying due to air/gas bubbles, which burst. The bursting bubbles form small craters or holes, which fail to coalesce before the film dries.
- 26. Pinholes • Common Causes •Solvent or air entrapment • Incorrect spray application • Incorrect solvent blend • Remediation • Abrade • Clean • Recoat
- 27. Holidays • Similar topinholes (used interchangeably) • Described as skips or misses in the coating system • Checked with holiday detector (right)
- 28. Holidays • Common Causes •Difficult application due to equipment access • Poor workmanship • Remediation • Abrade • Clean • Recoat
- 29. Fisheyes • Small crater-like openingsthat form during application or shortly after
- 30. Fisheyes • Common Causes •Poor surface preparation • Contamination • Use of a thinner instead of solvent cleaner • Remediation • Abrade • Clean • Solvent cleaning • Recoat
- 31. Wrinkling • Wavy linesthat appear in the paint film during different stages of coating application
- 32. Wrinkling • Common Causes •Excessive application of paint • Actual temperatures exceeding or going below application range • Overcoating before previous coat has sufficiently hardened • Remediation • Abrade • Clean • Recoat
- 33. Dry Spray • Arough or uneven finish in the paint film, were particles are not fluid and flowing together
- 34. Dry Spray • CommonCauses • Improper application technique • Actual temperatures exceeding application range • Remediation • Ensure proper distance of the spray gun to the substrate is being achieved
- 35. Summary • There aremany reasons why coatings may fail. The inspector investigates and identifies the cause of coating failure so that it can be remediated
- 36.