Marine Coatings Are Used in Some of the Harshest Environments

Ships operate in extremely harsh environments.

Seawater.
Salt.
Ultraviolet radiation.
Moisture.
Waves.
Abrasion.
Biofouling.
Temperature changes.
Atmospheric pollutants.

They are continuously exposed to these effects over long periods.

Marine coatings therefore require more than an attractive appearance.
The film must protect the hull from corrosion, limit marine-organism attachment, and reduce repair or maintenance burdens.

Marine coatings do more than provide appearance.
They are coatings that support hull life, operating efficiency, safety, and maintenance costs.

This approach also applies to port equipment, offshore structures, coastal steel structures, and outdoor equipment.

Different Areas of the Same Hull Face Different Environments

Do not treat the entire hull as a single environment when considering marine coatings.

The stresses vary considerably between locations on the same ship.

Consider the following main categories separately.

• Areas exposed to the atmosphere
• Areas immersed in seawater
• The seawater/atmosphere boundary zone
• The hull bottom
• The deck
• Areas around the engine room
• Ballast tanks and internal structures

Atmospherically exposed areas face ultraviolet radiation, rain, salt, and temperature changes.
Immersed areas face seawater, salt, water pressure, biofouling, and abrasion.
At the seawater/atmosphere boundary, repeated action of moisture, oxygen, and salt promotes corrosion.

Marine coatings therefore require separating deterioration factors by location and varying coating specifications accordingly.

Weather Resistance and Corrosion Protection Matter in Atmospheric Exposure

Weather resistance is important for hull areas exposed to the atmosphere.

Weather resistance is the ability to withstand outdoor conditions.
It means the film resists deterioration from ultraviolet radiation, rain, moisture, temperature changes, and atmospheric contamination.

The following defects are particularly common in atmospherically exposed marine coatings.

• Fading
• Gloss loss
• Chalking
• Cracking
• Rust
• Blistering
• Delamination
• Dirt deposition

Chalking is surface deterioration that produces a powdery appearance.
It is common in outdoor coatings exposed to ultraviolet radiation and rain.

Topcoat weather resistance matters in atmospheric exposure.
However, the topcoat alone may not be sufficient.

Primer rust protection.
Intermediate-coat barrier performance.
Appropriate film thickness.
Pretreatment.
Recoating intervals.
These combine to determine long-term durability.

Corrosion Protection and Antifouling Matter in Seawater

Immersed areas demand extremely high coating-film performance.

Corrosion protection is the first important requirement.

Seawater contains salt.
Salt and moisture acting on metal surfaces promote corrosion.

Scratches, pinholes, or insufficient thickness allow seawater to penetrate the film and initiate corrosion.

Biofouling is another problem in seawater.

Marine organisms such as shellfish, algae, and barnacles may attach to the hull bottom or seawater-contact areas.
Their attachment roughens the hull surface and increases water resistance.

Greater resistance increases fuel consumption and reduces sailing efficiency.

Hull-bottom coatings therefore require antifouling performance as well as corrosion protection.

Antifouling Paint Also Affects Operating Efficiency

Antifouling paint limits the attachment of marine organisms.

Biofouling on the hull bottom does more than impair appearance.
It increases resistance as the hull travels through water.

This causes the following problems.

• Higher fuel consumption
• Lower sailing speed
• Higher operating costs
• More frequent maintenance
• Greater hull-bottom cleaning burden

Hull-bottom coating therefore also contributes to energy saving.

Coatings provide more than protection or appearance.
On ships, film condition affects fuel consumption and operating efficiency too.

This is an extremely important perspective for CoatureVietnam’s Helpful Information.

Coatings affect product operating costs and energy efficiency too.

This approach also applies to factory or conveying equipment outside the marine sector.

Corrosion Progresses Readily at the Seawater/Atmosphere Boundary

The seawater/atmosphere boundary is one ship area requiring particular attention.

It experiences repeated wetting and drying.
Moisture, oxygen, and salt readily act together there.

Because the conditions needed for corrosion readily coincide, deterioration progresses quickly.

This matters for port equipment and offshore structures as well as ships.

Examples include the following areas.

• Pier steelwork
• Lower sections of port cranes
• Equipment exposed to seawater spray
• Coastal steel frames
• Areas around seawater pumps
• Aquaculture equipment
• Drainage equipment
• Water-treatment equipment

Fully immersed and completely dry areas require different coating specifications.
Areas repeatedly wetted and dried require more careful corrosion-protection design.

Surface Preparation Determines Marine-Coating Corrosion Protection

Surface preparation is extremely important for protective coatings on ships and marine equipment.

Even high-performance protective paint cannot fully perform if rust, oil, salt, or dirt remains on the steel surface.

Residual salt is a major issue in marine environments.

Salt remaining before application may promote corrosion beneath the film.
It may also cause poor adhesion or blistering.

Check the following in surface preparation.

• Has rust been removed?
• Is the surface free from oil?
• Has salt been removed?
• Is surface roughness appropriate?
• Is the surface free from dust?
• Is blasting adequate?
• Is the time until application controlled?

Surface condition before application strongly determines long-term marine-coating durability, as well as paint performance.

Film-Thickness Control Is Important in High-Build Coating

Ships and offshore structures may require relatively thick films to achieve corrosion protection.

However, greater thickness is not necessarily better.

Insufficient thickness means insufficient corrosion protection.
Excessive thickness, however, may cause sagging, poor drying, cracking, insufficient curing, or poor intercoat adhesion.

Consistently achieve the specified thickness in the required areas.

The following locations require particular attention.

• Edges
• Corners
• Welds
• Around bolts
• Recesses
• Rear surfaces
• Areas where water collects
• Areas exposed to waves or abrasion

Measuring only flat-surface thickness is insufficient.
Focus checks on vulnerable areas where corrosion tends to start.

Underwater Repairs May Be Necessary

Ships and offshore structures cannot always be repaired on land.

Large ships or marine equipment may need repairs while in service.
Repair materials or paints that cure underwater are therefore sometimes used.

Underwater repair involves an entirely different approach from ordinary coating.

Ordinary coating assumes dry surfaces, suitable temperatures, and controlled conditions.
Underwater repair must instead assume the presence of water.

The following checks matter in these specialized repairs.

• Can the material cure underwater?
• Can it adhere to wet surfaces?
• Can the repair area be surface-prepared?
• Can the work be performed quickly?
• Is durability after repair sufficient?
• Can the work be performed safely?

Underwater repair is specialized, but it offers an important lesson.

That lesson is that coating and repair must be considered according to the service environment.

Maintenance Planning Also Matters in Marine Coating

Marine coating does not end with the initial application.

Ships remain in use for long periods.
Films gradually deteriorate.
Scratches occur.
Organisms attach.
Localized corrosion develops.

Inspection, cleaning, repair, and recoating plans are therefore important.

Check the following items.

• What is the inspection interval?
• Which areas need priority checks?
• At what stage should scratches or delamination be repaired?
• How long is antifouling performance maintained?
• What is the recoating interval?
• Will repairs require taking the ship out of service?
• What are the repair costs?

Consider long-term maintenance costs as well as initial prices in marine coatings.

This approach is shared by steel structures and outdoor equipment.

Marine-Coating Approaches Applicable in Vietnam

Vietnam is a coastal country with many coastal, port, shipping, marine-equipment, and seawater-related industries.

Marine-coating principles therefore apply to various fields.

Examples include the following.

• Ship components
• Port equipment
• Piers
• Seawater pumps
• Water-treatment equipment
• Steel frames in coastal factories
• Outdoor piping
• Equipment support frames
• Architectural metalwork in coastal regions
• Aquaculture-related equipment
• Container-related components

These products or equipment may be affected by salty air or moisture even without direct immersion in seawater.

Standard outdoor specifications may deteriorate prematurely, particularly in coastal areas.

CoatureVietnam can also apply marine-coating knowledge to coastal corrosion-protection proposals and outdoor-equipment improvements.

Marine and Coastal Risks to Consider in Vietnam

Vietnam’s marine and coastal environments involve the following risks.

• Heat and humidity
• The rainy season
• Salty air
• Strong ultraviolet radiation
• Typhoons or strong winds
• Outdoor storage
• Seawater spray
• Abrasion of port equipment
• Delayed equipment repairs
• Variations in on-site repair quality

Corrosion progresses particularly readily where salt and moisture act together.

Ultraviolet deterioration from strong sunlight also requires consideration.
For outdoor equipment, topcoat weather resistance matters as well as corrosion protection.

Coating proposals for ships, ports, and coastal equipment in Vietnam should encompass surface preparation, film thickness, repairs, storage, and inspection, as well as paint selection.

CoatureVietnam’s 4M Checks

CoatureVietnam checks coatings for ships and marine environments through the 4M perspective.

Material: Materials

• Is the protective paint suitable for seawater immersion?
• Is antifouling paint necessary?
• Is a weather-resistant topcoat needed for atmospheric exposure?
• Does the specification suit splash or boundary zones?
• Are underwater repair materials necessary?
• Is the primer, intermediate coat, and topcoat combination appropriate?
• Is it compatible with repair paints?
• Can it withstand salt-damage environments?

Method: Methods

• Is the surface-preparation method appropriate?
• Has surface salt been removed?
• Is each layer’s thickness controlled?
• Are recoating intervals followed?
• Is sufficient curing time provided before seawater exposure?
• Are specifications differentiated by location?
• Are repair procedures standardized?

Machine: Equipment

• Is blasting equipment available?
• Can the application equipment handle high-build coating?
• Is there space to coat large members?
• Are ventilation and safety measures sufficient?
• Can humidity or weather effects be controlled?
• Is a film-thickness gauge available?
• Is equipment needed for underwater repairs available?

Man: People

• Do operators understand the differences between immersion, atmospheric exposure, and boundary zones?
• Do they understand the importance of salt removal?
• Do they understand that insufficient thickness causes corrosion?
• Do they understand that antifouling coatings affect fuel consumption and operating efficiency?
• Do they understand repair-work standards?
• Do supervisors know inspection intervals and repair plans?

The Management perspective requires clarifying design life, recoating intervals, repair costs, risks of taking ships out of service, and warranty scope.

Questions to Ask During Customer Visits

The following questions are useful for ship, marine-equipment, and coastal-component coating projects.

• Will this product be immersed in seawater?
• Is this area exposed to the atmosphere?
• Is this area exposed to seawater spray?
• Will it be used in a coastal region?
• Which is more important: corrosion protection or antifouling?
• Are there biofouling problems?
• How long should it operate without recoating?
• What surface-preparation method is used?
• Is surface salt controlled?
• Where is film thickness measured?
• Can repairs be performed on land, or are underwater repairs needed?
• Are the effects of film deterioration on fuel consumption or operating efficiency considered?

These questions help develop coating specifications suited to the service environment, beyond simply selecting rust-preventive paint.

Conclusion: Marine Coating Requires Understanding the Environment at Each Location

Different locations on the same hull require different performance.

Atmospheric exposure requires weather resistance and corrosion protection.
Seawater immersion requires corrosion protection and antifouling.
The seawater/atmosphere boundary requires careful specification design because corrosion progresses particularly readily.
Preventing biofouling and reducing water resistance at the hull bottom also affect fuel consumption and operating efficiency.

Marine coatings do more than improve appearance.

They protect the hull, maintain operating efficiency, reduce repair burdens, and support safety.

CoatureVietnam regards marine-coating principles as important corrosion-protection technology applicable to port equipment, coastal steel structures, outdoor equipment, and marine-related components too.

Coating the Future with Science and Care

Putting this into practice means understanding differences between seawater, atmospheric, and boundary-zone environments and proposing coating improvements that support customers’ product life and maintenance costs.