Premature Corrosion of Powder-Coated Rainscreen Panels
Significant areas of corrosion were identified on aluminium rainscreen panels only eight years after installation. Investigation indicated that the powder-coating thickness was below the specified requirement, resulting in inadequate protection of the aluminium substrate. This allowed moisture and environmental contaminants to penetrate the coating, causing premature surface corrosion and deterioration across several areas.
- NCQLE reference
- NCQLE-2026-00013
- Quality topic
- Product compliance
- Lesson type
- Failure
- Evidence rating
- Experience
- Published
- 1 August 2026
- Last reviewed
- 1 August 2026
Evidence basis: Supported by relevant professional experience. This learning is provided for professional consideration and does not replace project-specific competent advice, statutory duties or contractual requirements.
Context
The issue was identified during an inspection of an occupied building’s external rainscreen façade approximately eight years after completion. Powder-coated aluminium panels had been installed as the visible outer weathering layer and would normally be expected to provide a durable, low-maintenance finish for considerably longer. The premature deterioration raised concerns regarding manufacturing quality, coating compliance, long-term appearance and the remaining service life of the panels. During inspection, widespread white corrosion deposits, blistering and deterioration were observed across the surface of several powder-coated aluminium rainscreen panels. The panels were only approximately eight years old. Testing indicated that the powder-coating thickness was below the specified requirement, leaving the aluminium substrate inadequately protected and allowing moisture and contaminants to cause premature corrosion.
The transferable lesson
Powder coating must be treated as a critical protective system, not simply a decorative finish. The specified coating thickness, surface preparation and application quality must be verified during manufacture before panels are delivered. Inadequate coating thickness can allow moisture and contaminants to reach the aluminium substrate, resulting in premature corrosion, costly remediation and a significantly reduced service life.
Recommended action
Specify the required powder-coating system, surface preparation and minimum coating thickness for the intended environment. Use an approved applicator and require factory quality-control records, including coating-thickness measurements for each production batch. Approve a benchmark sample, undertake independent spot checks before delivery, and reject panels with thin, inconsistent or damaged coatings. Protect panels during transport and installation, repair approved minor damage correctly, and retain all inspection records, warranties and maintenance requirements within the project’s quality documentation.
Limitations and application
This lesson applies primarily to powder-coated aluminium panels exposed to external environmental conditions. Visual appearance alone cannot confirm inadequate coating thickness or determine the complete cause of deterioration. Conclusions should be supported by calibrated thickness measurements, adhesion testing, coating analysis and a review of the original specification and manufacturing records. Other factors, including poor surface preparation, coating damage, aggressive cleaning, salt exposure, trapped moisture or galvanic interaction, should also be investigated before deciding on repair or replacement.