What is the most commonly used method for corrosion protection in the splash zone?
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The splash zone is the area in marine environments where corrosion is most severe, with corrosion rates that can be 3 to 10 times higher than those in fully submerged areas. Conventional protective coatings for atmospheric zones or electrochemical protection for fully submerged areas are not very effective in protecting this area. The most commonly used protection methods in the industry include the following: First, heavy-duty anti-corrosion coatings, which use thick and durable protective layers to isolate the substrate from corrosive agents such as seawater and oxygen. This is a widely used basic protection method in splash zones; however, it requires high standards for surface treatment of the substrate, and over time exposure to ocean waves can lead to bubbling and peeling problems. II. Coating anti-corrosion technology: This is the most advantageous and well-developed core protection method for splash zones at present. Among them, the multi-layer rosin coating anti-corrosion technology (PTC) is the most widely used technique in China. It consists of four layers: rosin anti-corrosion paste, rosin anti-corrosion tape, a sealing buffer layer, and a fiberglass protective cover. It can be applied while there is water present, requires minimal surface preparation, and offers a protection lifespan of over 30 years; it has been included in standard GB/T 32119-2015. This technology has been demonstrated in nearly a hundred major marine engineering projects, including the Hong Kong-Zhuhai-Macao Bridge, Shengli Oil Field, offshore wind power projects, and Qingdao Port. It is the mainstream solution for addressing the corrosion problem in splash zones. III. Metal coating + sealing: Metal spraying techniques such as hot-dip zinc spraying and hot-dip aluminum spraying are used, followed by the application of a sealing coating to provide dual protection, which significantly enhances corrosion resistance. This approach is often combined with other protective measures and is suitable for components in splash zones with relatively simple structures. In addition, corrosion-resistant alloy coatings and oxidation polymer coating anti-corrosion technology (OTC) are also used in specific applications, further expanding the options available for protecting the splash zone.
After reading the useful information shared by the original poster, it’s true that corrosion protection in splash zones is a long-standing challenge. I would like to add some insights from my own practical experience: regarding the heavy-duty anti-corrosion coatings mentioned by the original poster, in addition to the high requirements for surface treatment, the combination of different coating components is also crucial. For example, combinations such as an epoxy primer plus a polyurethane topcoat offer significantly better long-term adhesion in splash zones compared to applying a thick single layer. Coating anti-corrosion technology is indeed being used more and more often these days. However, it is important to ensure proper sealing of the coating material with the steel substrate, especially at welds and joints; water infiltration there can accelerate corrosion. I’ve seen several cases where failure occurred due to poor attention to this detail. If conditions permit, a composite protection scheme (coating + encapsulation + appropriate sacrificial anode) will result in a longer service life; however, the choice of specific approach depends on the maintenance schedule and budget of the shipowner or platform – there is no universal solution. The information mentioned by the original poster is already very comprehensive. From the perspective of actual construction, quality control during the building process often plays a more decisive role in determining success or failure than the specifications of the materials themselves.