ALKA-9938 

Marine Atmospheric Protective Coating System

Premium three-coat corrosion protection system designed for above-water marine and coastal steelwork exposed to salt-laden atmosphere, high humidity, condensation, severe weathering and continuous UV exposure.

PROTECTION STRATEGY

ALKA-9938 uses a:

Zinc-Rich Primary Protection → High-Build Epoxy Barrier → UV-Stable Polyurethane Weathering Finish

strategy.

Each coating performs a separate and complementary function.

Zinc-Rich Epoxy Primer

ALKA-404 provides the primary corrosion-protection layer directly over correctly prepared carbon steel.

High-Build Epoxy Barrier

ALKA-413 creates the principal physical barrier between the primed steel and the marine atmosphere, increasing total system film thickness and reducing penetration of moisture and atmospheric contaminants.

Polyurethane Weathering Finish

ALKA-421 protects the underlying epoxy system from direct exterior exposure while providing improved UV stability, colour retention and finished appearance.

This layered strategy is particularly important in marine environments because corrosion protection cannot depend on a decorative finish coat alone.

KEY PERFORMANCE BENEFITS

• Premium three-coat marine-atmospheric protection system
• Specifically designed for above-water coastal and marine steelwork
• Zinc-rich epoxy primary corrosion protection
• High-build epoxy intermediate barrier
• UV-resistant polyurethane exterior finish
• Suitable for salt-laden atmospheric exposure
• Suitable for high-humidity coastal environments
• Designed for repeated atmospheric wet/dry cycling
• Suitable for steel exposed to condensation and rainfall
• High total protective film build
• Good long-term colour retention
• Good exterior appearance retention
• Suitable for visible marine infrastructure
• Suitable for difficult-to-access structural steel
• Suitable for high-value port and harbour assets
• Suitable for new marine construction and major refurbishment
• Strong combination of corrosion protection and exterior durability
• Suitable where future maintenance access may be expensive
• Clear separation from specialist splash, tidal and immersion systems

COAT 1 — ALKA-404 Zinc-Rich Epoxy Primer

Function: Primary Corrosion-Protection Primer

ALKA-404 is applied directly to correctly prepared carbon steel and forms the foundation of ALKA-9938.

Its role is particularly important in marine-atmospheric environments because the steel/coating interface requires robust primary protection against aggressive chloride-containing exposure.

The zinc-rich epoxy primer establishes the initial corrosion-protection layer before the high-build barrier coats are applied.

Product: ALKA-404 Zinc-Rich Epoxy Primer
Position: Directly over abrasive-blasted carbon steel
Primary Function: Primary corrosion protection
Nominal DFT: To project specification and current ALKA TDS

COAT 2 — ALKA-413 High-Build Epoxy

Function: Principal Marine Atmospheric Barrier Coat

ALKA-413 forms the principal high-build barrier layer within ALKA-9938.

The epoxy intermediate coat increases the total protective film thickness and creates a substantial physical barrier between the zinc-primed steel and the external marine environment.

This layer is particularly important for reducing the ability of:

• Moisture
• Condensation
• Atmospheric salts
• Oxygen
• Industrial/coastal contaminants

to reach the underlying substrate.

Product: ALKA-413 High-Build Epoxy
Position: Intermediate barrier coat
Primary Function: High-build barrier protection
Nominal DFT: To project specification and current ALKA TDS

COAT 3 — ALKA-421 Polyurethane Finish

Function: UV-Resistant Marine Weathering & Appearance Coat

ALKA-421 forms the final exposed surface of ALKA-9938.

The polyurethane finish protects the epoxy system from direct sunlight and weather exposure while providing improved colour and gloss retention.

This is particularly valuable on visible marine structures such as wharves, terminals, port buildings, access structures and coastal industrial facilities.

Product: ALKA-421 Polyurethane Finish
Position: Final exposed coat
Primary Function: UV resistance, weatherability, colour retention and finished appearance
Nominal DFT: To project specification and current ALKA TDS

Nominal Total System DFT: Project-Specific

The final total system DFT should be established according to the marine exposure severity, project design life and current ALKA product technical data.

The specification should define the DFT of each individual coat rather than relying solely on an overall system thickness.

SUITABLE SUBSTRATES

ALKA-9938 is primarily intended for:

Abrasive-Blasted Carbon Steel

Typical assets include:

• Wharf superstructures
• Jetty superstructures
• Port structural steel
• Marine terminal steelwork
• Coastal structural frames
• Gantries
• Platforms
• Access structures
• Handrails
• Equipment supports
• Pipe racks
• Marine building steelwork
• Tank exteriors
• Coastal industrial infrastructure

Galvanised steel, stainless steel, aluminium and previously coated surfaces require separate assessment and potentially different primer selection.

SERVICE & EXPOSURE ENVIRONMENT

ALKA-9938 is specifically designed for marine atmospheric exposure above the splash and tidal zones.

Typical environmental conditions include:

• Salt-laden coastal air
• Airborne chloride deposition
• High relative humidity
• Frequent condensation
• Rainfall
• Repeated atmospheric wet/dry cycles
• Strong sunlight
• UV exposure
• Coastal winds
• Marine industrial contamination
• Exterior weathering

The system is particularly appropriate where steel is close enough to the sea to experience significant chloride contamination but is not directly subjected to regular seawater immersion or tidal cycling.

UNDERSTANDING MARINE EXPOSURE ZONES

Correct identification of the marine exposure zone is essential.

A marine structure may contain several fundamentally different exposure environments.

Atmospheric Zone

Steel located above direct seawater splash and exposed primarily to salt-laden air, humidity, rain and condensation.

ALKA-9938 is specifically designed for this zone.

Splash Zone

Steel repeatedly wetted by seawater spray, waves or severe splash.

This requires a more severe marine barrier system.

Tidal Zone

Steel repeatedly submerged and exposed as the water level changes.

This is a substantially more aggressive exposure and requires a dedicated system.

Immersion Zone

Steel permanently or predominantly submerged.

A specifically approved immersion coating system is required.

The same coating specification should not automatically be extended across all four zones.

TYPICAL APPLICATIONS

Wharf Superstructures

Above-water structural beams, columns, cross-members, platforms and support steelwork forming part of wharf infrastructure.

These structures can experience significant chloride deposition despite remaining above the direct tidal zone.

Jetty Superstructures

Structural steel located above the direct splash and tidal zones, including:

• Beams
• Platforms
• Access structures
• Support frames
• Handrails
• Equipment supports

Where structural elements extend downward into splash or tidal exposure, the coating specification should change at the defined exposure transition.

Port & Harbour Infrastructure

Above-water structural steel throughout ports and harbour facilities.

Typical applications include:

• Structural frames
• Access platforms
• Gantries
• Service structures
• Equipment supports
• Utility steelwork
• Loading-area structures

Marine Terminals

Externally exposed steelwork associated with bulk, container, fuel or industrial marine terminals.

Typical assets include structural frames, loading structures, service platforms and equipment-support steelwork located in marine atmosphere.

Coastal Industrial Facilities

Structural steel within industrial facilities located near the coastline and exposed to persistent salt-laden atmosphere.

Examples include:

• Processing facilities
• Coastal manufacturing plants
• Desalination facilities — atmospheric external steelwork
• Coastal utility facilities
• Port-side warehouses
• Marine maintenance facilities

Wharf-Side Warehouses & Buildings

External structural steel, frames, columns and visible steel components in buildings located immediately adjacent to marine environments.

Marine Equipment Support Structures

Frames and structural supports for equipment located in above-water marine environments.

This can include supports for:

• Pumps
• Mechanical equipment
• Electrical equipment
• Service equipment
• Loading systems
• Utility installations

Coastal Pipe Racks

External pipe racks and pipe-support structures exposed to coastal atmospheric conditions.

The system protects the structural steel supports; any process pipe coating should be selected according to its own operating conditions.

Above-Water Marine Gantries

Loading gantries, access gantries and fabricated steel structures located above direct seawater contact.

Marine Access Platforms & Walkways

Structural frames supporting platforms, walkways, ladders and access systems in marine facilities.

Tank Exteriors in Coastal Facilities

External shells, roofs and associated steelwork of storage tanks located in coastal or port environments.

This application refers to external atmospheric surfaces only.

Tank internals require a separate lining specification.

Coastal Bridges

Bridge steelwork located in coastal or salt-laden environments where the exposure remains atmospheric rather than direct tidal or immersion service.

SURFACE PREPARATION

Surface preparation is critical to the long-term performance of ALKA-9938.

Marine environments create an additional challenge because steel surfaces may contain soluble chloride contamination even when the surface appears visually clean.

Preparation should address:

• Rust
• Mill scale
• Oil
• Grease
• Dust
• Existing coatings
• Abrasive residues
• Chlorides
• Soluble salts
• Weld spatter
• Sharp edges
• Poor weld profiles
• Fabrication defects
• Moisture
• Condensation

Abrasive blasting should achieve the preparation standard and surface profile defined by the project specification.

SOLUBLE SALT & CHLORIDE CONTROL

Marine projects require particular attention to soluble surface contamination.

Chloride salts remaining beneath a coating system can contribute to premature coating failure and under-film corrosion.

Where required by the project specification, soluble salt testing should be undertaken after surface preparation.

If unacceptable contamination remains, additional cleaning and preparation may be required before coating.

This is particularly important during refurbishment of existing marine steel.

EDGE, WELD & FABRICATION DETAILING

Marine coating failures often begin at locations where film thickness is difficult to achieve.

Particular attention should therefore be given to:

• Sharp edges
• Welds
• Bolts
• Nuts
• Corners
• Brackets
• Crevices
• Steel connections
• Cut-outs
• Difficult-access areas

Edges should be appropriately treated and fabrication defects corrected before coating.

STRIPE COATING

Where required by the project specification, stripe coating should be applied to vulnerable details such as:

• Welds
• Edges
• Bolts
• Corners
• Brackets
• Complex connections

Stripe coating helps ensure adequate film build in areas where normal spray application may produce a thinner coating than on flat surfaces.

APPLICATION CONSIDERATIONS

Marine and coastal coating work requires careful environmental control.

Application should comply with the current technical data for ALKA-404, ALKA-413 and ALKA-421.

Important variables include:

• Ambient temperature
• Steel temperature
• Relative humidity
• Dew point
• Surface dryness
• Surface cleanliness
• Wind
• Salt deposition
• Mixing ratio
• Mechanical mixing
• Induction period where applicable
• Pot life
• Wet-film thickness
• Dry-film thickness
• Recoat intervals
• Cure conditions
• Protection from contamination between coats

Prepared or partially coated surfaces should not be allowed to become contaminated by marine salts before the next coating stage.

DEW POINT & CONDENSATION CONTROL

Coastal environments can experience rapid changes in humidity and steel temperature.

Condensation can form even when the surface does not initially appear wet.

Steel temperature and dew point should therefore be monitored before and during coating application according to the requirements of the relevant ALKA TDS and project specification.

Coating over condensation can severely compromise adhesion and long-term system performance.

RECOAT CONTROL

The correct recoat interval between:

ALKA-404 → ALKA-413 → ALKA-421

must be maintained.

Where the maximum recoat interval is exceeded, additional preparation may be required before applying the next coat.

The surface must also remain clean and free from:

• Salt
• Dust
• Overspray
• Oil
• Moisture
• Other contamination

between coating stages.

INSPECTION & QUALITY CONTROL

Specification-grade marine coating work should include documented inspection throughout the coating process.

Depending on project requirements, quality-control activities may include:

• Verification of abrasive-blast standard
• Surface-profile measurement
• Soluble-salt testing
• Visual inspection after blasting
• Environmental-condition monitoring
• Steel-temperature measurement
• Relative-humidity measurement
• Dew-point calculation
• Stripe-coat inspection
• Wet-film thickness measurement
• Dry-film thickness measurement
• Individual coat DFT verification
• Recoat-window verification
• Inspection for missed areas
• Inspection of welds and edges
• Final total system DFT measurement
• Final colour and appearance inspection
• Batch-number recording
• Application-condition records

For major marine infrastructure, inspection requirements should be defined before coating work begins.

WHY SPECIFY ALKA-9938?

ALKA-9938 should be specified when steel assets are exposed to a true marine or coastal atmosphere and require more than a general-purpose industrial coating system.

Its protection logic is:

ALKA-404 provides the zinc-rich primary protection at the steel interface.

ALKA-413 creates the substantial high-build epoxy barrier.

ALKA-421 provides the final UV-resistant weathering and appearance layer.

Together, these layers address the principal atmospheric challenges of marine infrastructure:

Chlorides + Moisture + Humidity + Condensation + Weather + UV

This makes ALKA-9938 particularly suitable for high-value coastal assets where corrosion failure would lead to expensive access, maintenance and disruption.

WHEN TO CHOOSE ALKA-9938

ALKA-9938 is particularly appropriate when:

• Steel is located close to the sea
• Airborne chloride exposure is significant
• The asset remains above the splash and tidal zones
• High humidity and condensation are expected
• Zinc-rich primary protection is required
• High-build epoxy barrier protection is required
• UV stability is important
• Colour retention is required
• The asset is visible
• Maintenance access is difficult or expensive
• A premium three-coat marine-atmospheric system is required

ALKA-9938 VS ALKA-9930

ALKA-9930 and ALKA-9938 use a similar premium three-coat protection philosophy.

However, their positioning is different.

ALKA-9930

is the broader Premium External Protective Coating System for exposed structural steel.

ALKA-9938

is specifically positioned for marine and coastal atmospheric exposure, with particular emphasis on chloride contamination, salt-laden air, high humidity and marine environmental control.

Therefore:

Premium general external steel protection → ALKA-9930

Dedicated marine/coastal atmospheric protection → ALKA-9938

ALKA-9938 VS ALKA-9933

ALKA-9933 is a high-barrier MIO atmospheric system where functional barrier protection is the main objective.

ALKA-9938 is a complete premium marine-atmospheric system with polyurethane finish.

Therefore:

Functional MIO high-barrier atmospheric protection → ALKA-9933

Premium marine protection + UV-stable finished appearance → ALKA-9938

ALKA-9938 VS ALKA-9939

This distinction is particularly important.

ALKA-9938

is designed for:

Marine Atmospheric Zone

Steel above the direct splash/tidal environment.

ALKA-9939

is designed for:

Splash & Tidal Zones

Steel exposed directly and repeatedly to seawater.

Therefore:

Salt-laden air / coastal atmosphere → ALKA-9938

Direct seawater splash / tidal cycling → ALKA-9939

On a single wharf or jetty project, both systems may therefore be specified on different sections of the same structure.

LIMITATIONS

ALKA-9938 should not automatically be specified for:

• Splash zones
• Tidal zones
• Permanent seawater immersion
• Submerged steel
• Internal ballast or process tanks
• Chemical tank lining
• Direct chemical containment
• Buried steel without specific assessment
• Substrates not approved for ALKA-404
• Existing coatings without compatibility assessment
• Areas where full marine surface preparation cannot be achieved without project-specific review

The exposure zone must be correctly identified before final system selection.

SPECIFICATION GUIDANCE

A complete ALKA-9938 project specification should define:

Substrate → Marine Exposure Zone → Surface Preparation Standard → Surface Profile → Soluble Salt / Chloride Limits → Edge & Weld Preparation → Stripe Coating → ALKA-404 Zinc-Rich Epoxy Primer → Primer DFT → ALKA-413 High-Build Epoxy → Barrier DFT → ALKA-421 Polyurethane Finish → Finish DFT → Total System DFT → Colour / Gloss → Environmental Limits → Dew Point Requirements → Recoat Windows → Inspection → Acceptance Criteria

For major marine projects, the coating schedule should clearly divide the structure into:

Atmospheric Zone → Splash Zone → Tidal Zone → Immersion Zone

and specify the appropriate coating system for each.

SYSTEM POSITIONING

ALKA-9938 should be presented to marine engineers, asset owners, port authorities and protective-coating contractors as:

A premium zinc-rich epoxy / high-build epoxy / polyurethane system specifically designed for long-term protection of above-water marine and coastal steelwork exposed to salt-laden atmosphere, humidity and UV weathering.

Its core value proposition is:

Zinc-rich primary protection + high-build epoxy barrier + UV-stable polyurethane finish + marine-specific atmospheric protection + long-term asset durability.

Application Examples

Atmospheric steelwork only; splash, tidal and immersion zones require separate assessment.

Coastal Bridge Steelwork

Photographic visuals on this page are AI-generated application illustrations, not completed ALKA projects. Colours are illustrative. The system schematic is conceptual and not to scale; refer to current ALKA technical data and project specifications.