7 Common Industrial Coating Defects: Causes and How to Prevent Them
Industrial coating defects can lead to rejected parts, production delays, excessive rework, and increased manufacturing costs.
Whether a manufacturer is applying liquid coatings to fabricated steel, machinery, equipment, or other metal components, maintaining a consistent finish requires control over multiple variables.
Coating chemistry, surface preparation, spray equipment, environmental conditions, and curing all influence the final result.
When defects appear, replacing the coating may not address the underlying problem.
Understanding the most common industrial paint defects and their potential causes can help manufacturers identify problems earlier and improve finishing consistency.
Here are seven coating defects manufacturers should recognize and evaluate.
1. Orange Peel
Orange peel describes a textured coating surface that resembles the skin of an orange rather than a smooth, uniform finish.
This defect occurs when the applied coating does not flow and level adequately before drying or curing.
Common potential causes:
Improper spray gun atomization.
Incorrect coating viscosity.
Excessive spray distance.
Inappropriate reducer or solvent selection.
Application or environmental conditions that limit coating flow.
How to address it:
Review spray equipment settings, coating viscosity, application technique, and the manufacturer's recommended reduction and drying conditions.
Improving atomization and allowing the coating to flow properly may help reduce surface texture.
2. Fisheyes and Cratering
Fisheyes are small, circular depressions where the coating pulls away from a localized area of the surface.
They are commonly associated with contamination that interferes with coating wetting.
Common potential causes:
Silicone contamination.
Oil or grease on the substrate.
Contaminated compressed air.
Residue from cleaning products.
Contamination introduced during handling or production.
How to address it:
Evaluate surface cleanliness, compressed-air quality, nearby contamination sources, and cleaning procedures.
Identifying and removing the source of contamination is generally more effective than repeatedly recoating affected parts.
3. Runs and Sags
Runs and sags occur when a liquid coating flows downward or accumulates unevenly before it has sufficiently dried or cured.
These defects can affect appearance and create inconsistent film thickness.
Common potential causes:
Excessive wet film thickness.
Improper spray gun movement.
Incorrect coating viscosity.
Inadequate flash time between coats.
Application conditions that slow drying.
How to address it:
Verify the recommended wet film thickness, review spray technique, and confirm that coating viscosity and application conditions meet the manufacturer's specifications.
Consistent operator technique can help reduce recurring runs and sags.
4. Pinholes and Solvent Popping
Pinholes are small openings or cavities in a coating film. Solvent popping may create tiny craters or ruptures when trapped volatile material escapes during drying or curing.
Although they can look similar, these defects do not always have the same cause.
Common potential causes:
Excessive coating thickness.
Inadequate flash-off time.
Rapid heating during curing.
Air or gas release from the substrate.
Improper mixing or application conditions.
How to address it:
Review film thickness, flash times, substrate condition, and curing schedules.
The correct solution depends on whether the defect results from trapped solvent, entrained air, substrate outgassing, or another source.
5. Blistering
Blistering appears as raised bubbles or localized swelling beneath or within the coating film.
Blisters can develop from moisture, contamination, corrosion, or other mechanisms that create pressure or weaken adhesion.
Common potential causes:
Moisture trapped beneath the coating.
Inadequate surface preparation.
Soluble salt contamination.
Improper pretreatment.
Exposure conditions incompatible with the coating system.
How to address it:
Examine the location and condition of the blisters, evaluate the substrate, and review preparation and pretreatment procedures.
Determining whether the blistering developed during application or after service exposure is an important part of troubleshooting.
6. Poor Adhesion and Peeling
Poor adhesion occurs when a coating fails to bond adequately to the substrate or to another coating layer.
The resulting failure may appear as peeling, flaking, or separation between coating layers.
Common potential causes:
Inadequate cleaning or surface preparation.
Incorrect pretreatment.
Incompatible primers or topcoats.
Contaminated substrates.
Improper curing or missed recoat windows.
How to address it:
Identify the layer where separation occurs and evaluate substrate preparation, coating compatibility, application procedures, and curing conditions.
Appropriate adhesion testing and coating inspection may help isolate the cause.
7. Dry Spray and Rough Finishes
Dry spray occurs when coating droplets partially dry before reaching the substrate or fail to flow together properly after application.
The resulting finish may feel rough, powdery, or uneven.
Common potential causes:
Excessive spray distance.
Improper atomizing pressure.
High ambient temperatures or rapid solvent evaporation.
Incorrect reducer selection.
Poor spray technique or equipment setup.
How to address it:
Review gun-to-part distance, atomization settings, coating formulation, and environmental conditions.
Correcting application variables can help improve coating deposition and finish uniformity.
How to Troubleshoot Recurring Industrial Paint Defects
When defects occur repeatedly, manufacturers should evaluate the entire finishing process rather than focusing on one variable.
A practical troubleshooting approach includes:
1. Identify the defect. Determine whether the issue is related to appearance, adhesion, film formation, or coating performance.
2. Determine when it occurs. Establish whether the defect develops during application, drying, curing, or after the finished product enters service.
3. Review recent changes. Examine changes in coating batches, surface preparation, equipment settings, operators, environmental conditions, or production procedures.
4. Inspect the application process. Evaluate mixing, spray settings, film thickness, fluid delivery, and curing conditions.
5. Test potential corrections. Use controlled trials to determine whether an adjustment improves the result without introducing new problems.
Documenting defects and process conditions can help identify patterns and reduce repeated troubleshooting.
Preventing Coating Defects Through Process Consistency
Many industrial coating problems are influenced by variation in production conditions.
Manufacturers can reduce unnecessary defects by establishing consistent procedures for:
Surface cleaning and pretreatment.
Coating mixing and preparation.
Spray equipment setup.
Wet and dry film thickness inspection.
Temperature and humidity monitoring.
Drying and curing verification.
Painter training and quality assurance.
Consistent processes make it easier to identify changes, maintain coating quality, and reduce avoidable rework.
How Industrial Coating Services Helps Manufacturers Solve Coating Problems
Industrial Coating Services (ICS) works with manufacturers to evaluate coating defects and identify practical improvements to their finishing processes.
With over 30 years of industrial finishing experience, our capabilities include:
Surface preparation and pretreatment evaluation.
Spray equipment and fluid-delivery support.
Painter training and application consistency.
Coating trials and quality assurance.
Finishing-process improvements.
Our approach considers the coating, equipment, and manufacturing process together.
The objective is to help manufacturers identify the underlying causes of coating problems rather than repeatedly addressing the symptoms.
Experiencing Recurring Industrial Paint Defects?
If your manufacturing operation is dealing with fisheyes, orange peel, runs, blistering, poor adhesion, or inconsistent finishes, ICS can help evaluate potential causes and recommend next steps.
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