GEN MARINE · TECHNICAL GUIDE
Marine Coating Systems Technical Guide
The steps to a long-lasting coating system on ships and marine structures, from system selection and surface preparation to film thickness control and dry-dock maintenance. The Gen Boya technical team supports you with project-specific specifications and site inspection.
APPLICATION STEPS
Measurable quality, lasting protection.
Sa 2½
SURFACE PREPARATION
40–75 µm
SURFACE PROFILE
≤ 50 mg/m²
SOLUBLE SALTS (NaCl)
+3 °C
ABOVE DEW POINT
≤ 85%
RELATIVE HUMIDITY
320 µm
BALLAST TANK DFT
01
System selection and specification
The right coating system is defined by the ship area, corrosivity category, target service life and the requirements of the owner and class society.
— Atmospheric zones are assessed as C5/CX and continuous immersion as Im2 according to ISO 12944-2.
— The specification defines product, number of coats, dry film thickness (DFT) and colour for each coat.
— For ballast tanks, IMO PSPC (MSC.215(82)) applies: 320 µm nominal DFT.
02
Surface preparation
The life of the coating system is directly related to surface quality. Preparation is inspected and recorded before application.
— Blast steel to ISO 8501-1 Sa 2½ with a profile of 40–75 µm.
— Use St 3 power-tool cleaning for local repairs.
— Remove weld spatter and burrs; round off sharp edges.
03
Salt and dust control
Soluble salts left on the surface cause osmotic blistering and early corrosion under the coating.
— Measure soluble salts per ISO 8502-6/9; the ballast tank limit is 50 mg/m² NaCl.
— Assess dust per ISO 8502-3 and vacuum-clean before application.
— Wash with fresh water to remove salts where required.
04
Climate conditions
Epoxy and polyurethane performance depends on climate conditions during application and curing.
— Steel temperature at least 3 °C above the dew point.
— Relative humidity below 85%.
— Record readings at the start of each shift and during the day.
05
Mixing and application
Correct mixing of two-component products determines the chemical and mechanical resistance of the film.
— Mix components A and B completely with a mechanical mixer; never mix partial quantities.
— Use within pot life; do not exceed the thinning limits in the data sheet.
— Select airless nozzle and pressure according to the data sheet.
06
Stripe coating
Edges and corners where spraying does not build enough film are where corrosion starts first.
— Brush-coat welds, edges, corners, holes and cut-outs separately.
— Apply a stripe coat before each full coat.
— The number of stripe coats in ballast and cargo tanks follows the specification.
07
Film thickness control
Film thickness is the measurable indicator of protection. Both low and excessive thickness reduce system performance.
— Check wet film thickness with a comb during application.
— Measure dry film thickness per ISO 19840; apply the 80/20 rule in general areas.
— Apply the 90/10 rule in ballast tanks; excessive thickness increases the risk of cracking.
08
Overcoating and curing
Each product has minimum and maximum overcoating intervals that govern intercoat adhesion.
— If the maximum interval is exceeded, roughen the surface.
— Tank coatings must be fully cured before service.
— Rinse potable water tanks after full cure before use.
09
Dry-docking and maintenance
Planned dry-dock maintenance extends coating life and reduces the need for full renewal.
— Wash the hull with high-pressure fresh water on docking and map damaged areas.
— Spot-blast or St 3 clean damaged areas and spot-prime with 605 Genepox Fast Primer.
— Use fast-drying, surface-tolerant systems for on-board maintenance.
10
Safety and environment
Work according to the product Safety Data Sheet (SDS) and shipyard safety procedures.
— Ventilate and gas-test tanks and confined spaces; use ex-proof equipment.
— Use respiratory protection, gloves, goggles and protective clothing.
— Dispose of blasting waste and paint residues according to regulations.