Coating Defects and Failures Presented by: Sarah Olthof

Topics Consequences of coating failure Role of coatings inspector in failure avoidance Common coating failures and defects

Scope This webinar describes the consequences of coating failures, field and laboratory investigative processes undertaken to diagnose coating failures, and reviews common coating defects and failures.

Learning Outcomes At the 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

Protective Coatings Principal material used for corrosion protection All coatings will breakdown over time Service life can be extended by performing maintenance painting once deterioration is identified

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

Once Premature Failure Occurs… 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?

Consequences of Coating Failures Financial impacts Litigation Substrate repair or replacement Costly rework and downtime

Substrate Repair or Replacement 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

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?

Role of a Coating 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

Identification of a Non-Conformance The inspector: Identifies deficiencies as they arise Will work with contractor for reaction plan once non-conformance is identified

Common Coating Defects and Failures

Delamination Results from loss of adhesion between the substrate and coating OR between coats.

Delamination Common Causes Remediation 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.

Blistering Coating lifting from the underlying substrate

Blistering Common Causes Remediation Contamination on the substrate Oils and greases Soluble Salts (osmotic blistering) Solvent entrapment Remediation Ensure correct surface preparation and application Soluble salt testing

Blush Haze or oily residue on the surface of a coating

Blush Common Causes Remediation 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

Sags/Runs Downward movement of paint soon after application on vertical surfaces

Sags/Runs Common Causes Remediation 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

Orange Peel Pocked appearance; surface of paint film resembles the skin of an orange

Orange Peel Common Causes Remediation Poor application techniques Incorrect solvent blend Remediation Abrade Clean Recoat

Pinholes Formation of tiny 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.

Pinholes Common Causes Remediation Solvent or air entrapment Incorrect spray application Incorrect solvent blend Remediation Abrade Clean Recoat

Holidays Similar to pinholes (used interchangeably) Described as skips or misses in the coating system Checked with holiday detector (right)

Holidays Common Causes Remediation Difficult application due to equipment access Poor workmanship Remediation Abrade Clean Recoat

Fisheyes Small crater-like openings that form during application or shortly after

Fisheyes Common Causes Remediation Poor surface preparation Contamination Use of a thinner instead of solvent cleaner Remediation Abrade Clean Solvent cleaning Recoat

Wrinkling Wavy lines that appear in the paint film during different stages of coating application

Wrinkling Common Causes Remediation Excessive application of paint Actual temperatures exceeding or going below application range Overcoating before previous coat has sufficiently hardened Remediation Abrade Clean Recoat

Dry Spray A rough or uneven finish in the paint film, were particles are not fluid and flowing together

Dry Spray Common Causes Remediation Improper application technique Actual temperatures exceeding application range Remediation Ensure proper distance of the spray gun to the substrate is being achieved

Summary There are many reasons why coatings may fail. The inspector investigates and identifies the cause of coating failure so that it can be remediated

QUESTIONS???