The Hidden Cost of Abrasive Methods on Hull Coatings

In-water hull cleaning is often treated as a necessary operational response to heavy fouling. However, when cleaning is performed reactively (after macrofouling is established) it typically requires aggressive mechanical force. The result is not just fouling removal, but coating damage, increased roughness, higher fuel consumption, and long-term economic and environmental consequences.

This page explains:

• Why reactive cleaning causes coating degradation
• How abrasive methods increase hydrodynamic roughness
• The measurable fuel and emissions penalties
• Why proactive grooming is fundamentally different

Reactive Cleaning: Why It Becomes Abrasive

Biofouling develops in stages:

1. Biofilm (slime) formation
2. Microfouling
3. Macrofouling (barnacles, tubeworms, mussels, calcareous growth)

Once calcareous macrofouling is established, removal requires high mechanical force. According to Swain et al. (2022), reactive in-water cleaning is typically performed “once fouling has reached significant levels” and requires “powerful machinery which damages the coatings” .

The key problem:

Removing hard fouling requires forces high enough to exceed the cohesive or adhesive strength of the coating surface.

This can lead to:

• Ablative layer removal
• Silicone fouling-release surface scarring
• Increased surface roughness
• Premature coating depletion
• Increased biocide release (in copper systems)

Coating Damage and Increased Surface Roughness

Hull coatings are engineered systems:

• Self-Polishing Copolymer (SPC)/Ablative AF coatings rely on controlled surface erosion.
• Fouling Release Coatings (FRCs) depend on ultra-smooth, low-surface-energy finishes.

Abrasive cleaning disrupts both systems.

Swain et al. (2022) document that reactive cleaning results in:

• “Excessive discharges of paint and biofouling”
• Coating damage
• Increased environmental release .

When coating surface integrity is compromised, hydrodynamic roughness increases. Even small increases in equivalent sand-grain roughness (ks) significantly increase frictional resistance.

The IMO GloFouling report (2022) clearly connects hull roughness to increased hydrodynamic drag, fuel consumption, and GHG emissions . 

Why Roughness Matters

Resistance increase is not linear. As surface roughness increases:

• Frictional resistance rises
• Required shaft power increases
• Fuel consumption increases
• CO₂ emissions increase

Even light slime can cause measurable efficiency penalties. Macrofouling and coating roughness increase the penalty substantially .

The Economic Consequences of Roughness

The economic impact of biofouling has been rigorously quantified.

Schultz et al. (2011) analyzed the cost impact of hull fouling on a U.S. Navy destroyer and found:

• The primary cost driver associated with fouling is increased fuel consumption.
• Cleaning and painting costs are small compared to fuel penalties.
• For the DDG-51 class, fouling-related fuel costs were estimated at $56M per year (class-wide) .

The implication is critical:

Any cleaning method that increases long-term hull roughness increases lifetime fuel cost.

Abrasive reactive cleaning may remove fouling—but if it increases coating roughness, it embeds an ongoing fuel penalty. EverClean is an approved hull grooming solution for use with GIT Coatings and Chugoku Marine Paints.

Abrasive Cleaning and Coating Life Reduction

Reactive cleaning can also shorten coating service life.

Swain et al. (2022) highlight that cleaning after calcareous fouling develops requires “fairly high forces that may damage the coating” .

This damage can result in:

• Accelerated coating depletion
• Premature drydock
• Increased lifecycle coating cost
• Increased paint discharge to the environment

In contrast, proactive grooming was defined as:

“Gentle, habitual and frequent mechanical maintenance… with minimal impact to the coating” .

The distinction is force threshold and frequency.

Environmental Impacts of Reactive Cleaning

Reactive abrasive cleaning has several environmental consequences:

1. Paint Particle Discharge

Damaged coatings can release:

• Copper (in biocidal systems)
• Polymer fragments
• Microplastics

Swain et al. (2022) note that reactive cleaning can produce excessive discharge requiring capture and disposal in some jurisdictions .

2. Increased GHG Emissions

Roughened surfaces increase fuel burn. The IMO GloFouling analysis shows that unmanaged biofouling can increase GHG emissions significantly depending on severity .

3. Invasive Species Risk

Waiting until macrofouling establishes increases the risk of species transport between regions .

Reactive vs. Proactive: The Force Threshold Problem

Research at the Naval Postgraduate School (Royster, 2022) evaluated proactive grooming frequencies across temperature and biome conditions. The study found that:

• Grooming is effective when performed at appropriate frequency.
• Properly executed grooming controls fouling without coating degradation.
• Frequency should be tailored to local fouling pressure and temperature .

The key technical insight:

There is a narrow “grooming zone” where fouling can be removed without exceeding coating damage thresholds.

Reactive cleaning operates outside this zone. Proactive grooming, such as EverClean, operates within it.

Real-World Examples: Severe Fouling and Coating Condition

Service reports from reactive cleanings frequently document:

• Heavy barnacle coverage
• Severe coating wear and detachment
• Inability to inspect due to calcareous fouling

For example, a 2022 hull cleaning report documented paint in “POOR condition showing severe worn out and detachment” in areas heavily fouled .

When macrofouling must be mechanically removed from an already degraded coating, coating life is further compromised.

The Technical Conclusion

Reactive, abrasive hull cleaning creates a cascade of consequences:

In contrast, proactive, low-force grooming:

• Removes slime before macrofouling establishes
• Maintains hydrodynamic smoothness
• Preserves coating integrity
• Minimizes discharge
• Reduces fuel penalties

References

• Swain et al., Proactive In-Water Ship Hull Grooming as a Method to Reduce the Environmental Footprint of Ships
• GEF-UNDP-IMO GloFouling Partnerships, Analysing the Impact of Marine Biofouling on the Energy Efficiency of Ships
• Schultz et al., Economic Impact of Biofouling on a Naval Surface Ship
• Royster, Temperature and Biome Effects on Proactive Grooming Frequencies