Under China's "Maritime Power" strategy, offshore wind power is moving from nearshore to deep and far seas. Unlike onshore wind turbines, offshore towers and foundations are长期处于 extreme corrosive environments with high salt spray, high humidity, and strong UV — about 3.5% sodium chloride in seawater turns into salt spray with sea breeze, and chloride ion content is over 10 times that of inland industrial environments, which can easily penetrate ordinary coatings to reach the steel and destroy the passive film, causing severe pitting corrosion. Measurements show that the corrosion rate of offshore wind towers can be 5–10 times that on land.
I. Why can't traditional topcoats last 25 years?
Offshore corrosion is a superposition of multiple mechanisms. The first is chloride ion pitting: highly penetrating chloride ions destroy the steel passive film and then form occluded cells at coating defects, accelerating autocatalytically. The second is crevice corrosion: accumulated water in crevices of tower flanges, bolt connections, and weld edges is the weak point where ordinary coatings most easily fail. The third is UV degradation and thermal stress: offshore areas are unshielded, UV intensity is over 30% higher than inland, accelerating coating chalking and cracking; day-night and seasonal temperature differences cause towers to frequently expand and contract thermally, further tearing the coating. The fourth is wave splash and microbial attachment, which is especially destructive to the splash zone and tidal zone.
Traditional polyurethane topcoat in such environments usually chalks, cracks, and peels within 3–5 years. Once failed, the tower rusts rapidly and wall thickness thins, directly threatening the structural safety of the unit. Offshore maintenance is extremely difficult: it requires large lifting vessels and aerial work platforms, with a single maintenance cost up to several million yuan, and the unit shutdown during maintenance causes huge power generation losses. Industry statistics show that among the full-lifecycle maintenance cost of offshore wind towers, anti-corrosion maintenance accounts for over 60%. More tricky is that corrosion often starts from internal weld seams and flange crevices; by the time external rust is visible, structural damage is already irreversible.
II. Coating system design to meet 25-year service life
The core idea is differentiated matching by corrosion zone. Taking the titanium-based graphene heavy anti-corrosion system as an example, the marine atmospheric zone (tower outer surface) uses cold spray zinc primer 80μm + marine heavy anti-corrosion primer 150μm + heavy anti-corrosion topcoat 120μm, total dry film about 350μm; splash and tidal zone (jacket, pile foundation) total dry film thickened to 600μm; full seawater immersion zone is 320μm. This system has artificial accelerated aging ≥5000h (traditional polyurethane ≤1000h), salt spray resistance ≥5000h (traditional epoxy zinc-rich ≤720h), adhesion ≥15MPa, hardness ≥6H, and is low VOC, using cold spray zinc instead of highly polluting hot spray zinc.
Another mainstream route is fluorocarbon topcoat. Wind-specific fluorocarbon paint uses polyvinylidene fluoride (PVDF) resin, with salt spray resistance over 3000h and artificial accelerated aging over 6000h; after curing the film is dense and pore-free, effectively blocking chloride ion penetration, and is regarded in the industry as a reliable topcoat choice for achieving 25-year tower life.
Europol International's EURONAVY system provides empirical evidence: primer + high-build intermediate coat + weather-resistant topcoat three-layer system, total dry film 600μm, in a northern offshore wind project after 10 years of operation the coating integrity rate exceeded 94%, evaluated by 25-year design life requiring no mid-term maintenance, saving the owner tens of millions of yuan. Dongfu Research Institute's DEC-DFY further passed NORSOK M501 certification, meeting the highest marine CX level, adhesion ≥5MPa, 4200h cyclic aging all grade 0, anti-corrosion life ≥25 years, and has been used in Shantou 18MW, Dongying 20MW and other key offshore wind projects.
Heavy anti-corrosion coating also needs collaborative design with cathodic protection. The underwater section of the tower is usually supplemented by sacrificial anodes or impressed current protection; if the coating undergoes cathodic disbondment, the protection current will surge and sacrificial anodes deplete prematurely, so the marine heavy anti-corrosion system must treat "cathodic disbondment resistance" as a core indicator, balancing adhesion and electrical insulation of the coating in the formulation.
III. Construction and inspection: long life is "coated" as well as "inspected"
No matter how good the formulation, it relies on a closed construction loop. Surface treatment must be sandblasted to Sa2.5, roughness 40–70μm, thoroughly removing scale and salt; factory coating mainly uses airless spray, strictly controlling temperature (≥5℃) and humidity (<80%); welds, edges, and corners must be pre-coated with emphasis to avoid edge rust first. Quality inspection covers dry film thickness, adhesion, and holiday (pinhole) detection — splash and immersion zones especially need holiday detection to ensure no through-pinholes. Later maintenance follows the rhythm of "inspect every six months in the first 2 years, then annually", using regular inspection to eliminate risks in the bud.
Different foundation forms (monopile, jacket, floating body) have different corrosion exposure, and matching thickness and coating types need targeted adjustment; deeper and farther seas with longer service and fiercer splash put higher demands on adhesion and cathodic disbondment resistance, which is exactly the direction of domestic coating technology iteration.
IV. The economic account behind long life
There is a counterintuitive truth in marine engineering anti-corrosion: initial coating cost is only about 15% of the full-lifecycle anti-corrosion total cost, while later maintenance accounts for over 80%. The 3–5 year maintenance cycle of traditional coatings means a 25-year project needs 4–7 maintenances, each costing 2–3 times the initial, plus shutdown losses, making the total cost huge.
Long-life coatings reduce maintenance to 1 or even zero times, cutting maintenance cost by over 40% alone, and avoiding multiple shutdown losses. More and more project parties have listed "anti-corrosion life" as a core bid evaluation indicator in tenders, no longer looking only at initial purchase price. This also contributes to low carbon — one less maintenance means one less old coating scraping, one less batch of solid waste and VOC emissions, fitting green low-carbon development requirements.
V. Kexin's marine anti-corrosion solution
For Kexin New Materials (Guangdong) Co., Ltd., offshore wind, sea-crossing bridges, and port machinery are all main battlefields of heavy anti-corrosion. It has deep accumulation in the heavy anti-corrosion coating system of epoxy zinc-rich primer, high-build intermediate coat, and weather-resistant topcoat, and can introduce the corrosion resistance of alloy paint and the dense film-forming idea of electroplating paint into marine scenarios. Facing the harsher conditions of deep and far seas, raising adhesion, salt spray resistance, and workability simultaneously is the necessary path for domestic coatings to move from "usable" to "25-year reliable".
VI. New questions for floating and deep-sea
As wind power moves to floating and farther deep seas, anti-corrosion is superimposed with new variables. The floating body bears dynamic alternating loads in waves, and the coating must remain crack-free under repeated bending and fatigue; biofouling (barnacles, algae attachment) near the waterline of the floating body destroys the film and accelerates local corrosion, forcing "anti-corrosion + antifouling" dual-function integration. Jackets and monopiles in deeper waters face stronger current scour, putting stricter demands on scour resistance and cathodic disbondment resistance.
This also changes the matching logic: deep-sea accessibility is poor and weather windows are short, a single construction must be "right the first time", sharply increasing requirements for coating reliability and construction tolerance. The material end therefore emphasizes high solid content, high-build, and long painting adaptation period; the design end takes "25-year maintenance-free" as a baseline, not a bonus. Whoever can hold adhesion and integrity under floating body dynamic conditions holds the ticket for the next leg of offshore wind.
It is worth noting that wind turbine enlargement makes monopile diameter exceed 10 meters and pile length over 100 meters; the factory coating of super-large components and transport bump protection are becoming new engineering bottlenecks restricting the realization of 25-year life, requiring cross-disciplinary collaboration between coatings and coating equipment.
Further reading: Nano Coating Technology: Principles, Preparation and Multi-field Applications · The Invisible Armor of New Energy Battery Packs and Energy Storage · Industrial Coating System Product Center