Requirements and applications of marine engineering heavy anti-corrosion coatings

Introduction
China is a large country with both land and sea, and the exploration of the sea has never stopped, from the initial benefits of fish salt, to the initial idea of sea rights, to the development of marine economy, innovation of marine science and technology, protection of the marine environment, construction of marine ecological civilization and a series of ideas put forward by the state in recent years, the development of the ocean has entered a shallow stage.
oil and gas resources are the key to coastal development, and coastal provinces and cities regard marine economic construction as an important strategic direction of marine economic development. Among them, not only drilling rigs, storage and transportation facilities, oil and gas pipelines, but also in recent years, the development of oil processing vessels, that is, mobile petrochemical

. We usually define a depth of 0 to 300 m as shallow water, 300 to 1,500 m as deep water, and 1,500 to 3,000 m as ultra-deep water. The construction cost of offshore equipment varies greatly according to the depth of water and offshore distance, maintenance, depreciation and operating costs are much higher than on land, and the anti-corrosion technology is more demanding and complex, because any shutdown or shutdown caused by the corrosion resistance of coatings will bring huge economic losses.
addition to offshore oil and gas development projects, in recent years, with the global focus on low-carbon clean energy, countries have set their sights on the wind power industry with huge wind resources. China has a long coastline, rich natural wind energy resources, although the wind power industry in the sea development started late, but the sea wind resources with its stability and power generation characteristics, the development of increasingly rapid. In recent years, China has also built a number of offshore wind farms along the coasts of Shanghai, Guangdong and other places. Like offshore oil platforms, offshore wind power facilities are also affected by sea breezes, salt spray, sun, tides and other factors.
The characteristics and requirements of anti-corrosion coating
the offshore project facilities are in a harsh environment, the required anti-corrosion technology is relatively complex, need to be decomposed according to different anti-corrosion requirements, so as to be targeted. The difficulty of corrosion prevention lies in the area above the sea surface, mainly by salt spray, sea air and wave splash corrosion, which usually refers to the area involving high water level up 1.5 m to low water level down 1 m, in this area the corrosion rate is high, is several times the atmospheric area and the total immersion area, the maximum corrosion area in the average sea water high tide level above 0.5 m.there are three main causes of severe corrosion in
:
(1) atmospheric factors: solar radiation, alternating wet and dry;
At the same time, the construction environment in this area is harsh, maintenance is difficult, the coating technology performance, construction performance requirements are very high, usually to meet the following requirements:
(1) can be wet, rust coating, can be on the low surface treatment of the substrate has a good attachment Focus; (2) can be underwater construction, underwater curing, (3) curing time is short, (4) construction methods can choose spraying or scraping, etc., (5) can have long-lasting corrosion resistance, (6) mechanical performance is excellent.
Seocal industry anti-corrosion related standards
At present, on fixed platforms, self-lifting platforms, auxiliary facilities and drilling vessels and other simple offshore facilities, the domestic design institute has the ability to design their own. FPSO, FLNG, large-scale semi-submers diving platform and other large-scale offshore facilities will be vigorously developed in the future, the domestic design institute is not yet able to design independently, feed design stage is usually the responsibility of foreign design companies, detailed design stage by domestic design institutes such as 708, offshore design department, etc. responsible, so the coating supporting design of offshore projects is very complex.
In the construction of offshore projects, the domestic petroleum and petrochemical design institute designed by the supporting multi-reference petroleum and petrochemical standards, in the face of domestic owners reference standards are:
(1) SY/T 4091-2018 beach offshore oil engineering external anti-corrosion technical specifications (2) SY/T 6930-2012 protective coating corrosion control of offshore structures, (3) GB/T 30790-2014 color paint and varnish protective coating system corrosion protection of steel structures.
designed by foreign offshore design institutes will usually be used in the same way as marine standards and offshore standards, usually including ISO12944, ISO 20340, NORSOK M501, NACE SP0108 and other standards.
offshore wind power industry, the main design institutes include East China Survey and Design Research Institute, Guangdong Electric Power Design Institute, Shanghai Survey and Design Research Institute, etc., will also basically refer to Norsok and ISO 20340 standard recommended coating supporting systems.
the performance requirements of ISO 20340-2009 (GB/T 31415) REQUIREMENTS FOR PROTECTIVE PAINT SYSTEMS FOR OFFSHORE AND RELATED STRUCTURES marine engineering and related structural protection coating systems. For marine engineering corrosion environment, it specifies the performance requirements of protective coating systems used in offshore buildings and related structures (i.e. those exposed to the ocean atmosphere and those immersed in salt water or brackish water), and this standard also applies to other construction structures using coatings or protective coating systems that meet this standard, defining three coating performance testing methods: cycle aging tests, seawater immersion tests, and cathode-resistant peeling tests.
ISO 12944-2017 (GB/T 30790) Paints and varnishes - Corrosion protection of steel structures by protective paint systems protects steel structures from corrosion protection. The standard clearly defines a variety of corrosion conditions and environmental types for protection with coating systems and coatings. Its purpose is to obtain appropriate and successful steel structure corrosion protection effect. ISO20340-2009 revised to include the latest version of ISO12944-2014 Part 9, redefining offshore based on the exposure of the environment can be combined C5-I and C5-M in the standard (CX) and immersion (IM4) two regions, in addition to two integrated areas between offshore (CX) and immersion (IM4), is the splash zone and tidal zone, and a set of certification test specifications is given.
surface treatment and coating of NONORSOK M501-2012 SURFACE DEVELOPMENT and PROTECTIVE COATING Marine Engineering. NORSOK standards are developed by the Norwegian oil industry to ensure that its development and operation are sufficiently safe, value-added (added value) and efficient use of funds. The standard replaces the technical specifications of oil companies as broadly as possible and can be used as an official regulation. For the protective coating used in the construction and installation of fixed or mooring offshore platforms, the selection of coating materials, surface treatment, construction process, coating inspection are put forward.
standards cover paint, metal coatings and steel structure fireproof coatings, using the ISO 20340 method. The three most important systems for offshore projects are:
(1) for corrosion protection on the outer surface of the atmospheric region, (2) 7A for corrosion protection in splash and tide differential areas, and (3) 7B for corrosion protection in underwater areas.
all of them require pre-certification by a third-party testing organization. The three coating performance test methods defined by ISO20340 are used respectively: cycle aging test, seawater immersion test and cathode-resistant peeling test for experiments, and after the experiment, the coating condition, adhesion, rust width at scratches and other data need to be examined in accordance with the requirements, which is the most stringent coating testing requirements in the coating industry.
THE NACE SP0108-2008 (SY/T6930) CORROSION CONTROL OF OFFSHORE STRUCTURES BY PROTECTIVE COATINGS uses coating protection to control corrosion of offshore steel structures. The standard gives the acceptance standard for the coating performance of the splash area, recommends the epoxy glass scale coating matching, its performance must meet:
(1) anti-corrosion spread, moisture-resistant heat cycle: <3.5mm (zinc-free primer coating system) ;(2) edge into Good membrane resistance; (3) heat resistance, no cracking; (4) good flexibility, impact strength > 5.6J (50in.1b) ;(5) cathode peeling: <7.0mm.
addition, a number of marine anti-corrosion evaluation criteria often cited are:
(1) NACE TM0104-2004 marine platform structure ballast water tank coating system assessment; external protective coatings; (3) NACE TM0304-2004 offshore platform structure atmospheric zone and fly zone coating system assessment; (4) NACE TM0404-2004 offshore platform structure atmospheric zone and fly zone coating system assessment.
high-performance epoxy coatings: marine anti-corrosion solutions
anti-corrosion coatings in the long-term normal work of marine equipment is particularly important. Breaking through the research and development technology and high cost bottleneck is the urgent task of the new technology of anti-corrosion of offshore engineering equipment. Previous standards recommend coating systems, such as epoxy and polyurethane coating systems recommended in Norsok and ISO20340, and epoxy glass scale coatings in NACE SP0108 are widely used in practical applications.
But the traditional coating system has its limitations such as slow drying, can not be thick coated, low temperature, moisture under the side reaction more, can not be underwater curing and underwater construction, poor cracking resistance, especially in the case of high and low temperature cycle is more serious. These lack of performance is not uncommon in offshore corrosion prevention projects, and a high-performance product is urgently needed to suit the broader environment.
At the same time, the first construction peak of offshore drilling rigs was in the mid-1970s and early 1980s, the service age of these offshore platforms is basically more than 30a, given its service life is usually 20 to 30a, the next few years the need for replacement is relatively large, will enter a peak. On the other hand, a considerable part of the platform in service requires local maintenance. According to statistics, HNOOC needs to refurbish more than 50 platforms, is currently at the rate of 10 per year for maintenance. Effective maintenance in such harsh environments is a challenge.
several difficulties need to be overcome in the maintenance process:
(1) can be cured underwater, local areas even need underwater construction;
in order to meet these requirements, the design of coating formulations, not only to consider the corrosion resistance of the coating, but also to take into account its construction performance.
problems with the admen of high-performance epoxy coatings. Marine corrosion protection, like ship corrosion protection, belongs to the marine corrosion protection environment. Early marine anti-corrosion, have followed the ship anti-corrosion products. In particular, ballast cabin paint in marine coatings, including universal primer, which is widely used in modern shipbuilding, has excellent corrosion protection and has been widely used in marine corrosion prevention. Norsok M501 Version 5 System 7 (anti-corrosion package for underwater and splash areas) also recommends companion solutions based on the ship's ballast cabin and underbody corrosion protection experience.
For the protection of marine splash zone, anti-corrosion experts learn from the successful experience of ice-zone navigation ships, the ultra-strong wear-resistant epoxy, epoxy glass scale coating applied to the splash zone, and achieved good results. However, due to the impact of maintenance/maintenance convenience, the requirements of marine anti-corrosion are much higher than ship anti-corrosion. Therefore, the general anti-corrosion performance and construction performance of marine coatings still can not meet the requirements mentioned earlier. Since the 1990s, international coatings companies have been introducing high-performance epoxy coatings specifically designed for offshore corrosion protection.
High-performance epoxy coating formulation using epoxy interoperability network enhancement technology, resin using small relative molecular mass epoxy to reduce its system viscosity, while with special amine curing agent to increase the cross-link density of the paint film, increase its water resistance, chemical resistance. The use of functional fillers such as jade, glass scales, so that it can get excellent physical performance and crack resistance, to maximize the protection of transport, work during the damage, reduce the installation site repair workload. Special additives can be added to increase the early water resistance of the paint film, to prevent the paint film after construction by splashing and waves.
Usually high-performance epoxy coating products should have the following characteristics:
(1) after spraying 30 min soaked sea water does not affect corrosion and adhesion performance, even underwater construction ;(2) fast-drying performance is excellent; (4) volume solid content >80%, can even reach 98% to 100%, can meet the requirements of a single thick coating, (5) recommended a single coating coating dry film 200 to 1,000 m, greatly shorten the construction cycle.
construction can choose a variety of spraying modes, to solve the problem of the applicable period, by adjusting the electronic ratio automatic control system online mixing, construction efficiency is high, a construction dry film thickness can reach 600 to 2,500 m, normal temperature drying 6 h, winter overnight can be moved, fast curing makes the construction can quickly resist the tide or wave attack.
High-performance epoxy coatings in the offshore industry application prospects
In recent years, with China's increasing attention to environmental protection issues, the formulation of a lot of strict VOC control measures and environmental regulations, China has also begun to green, environmental protection coatings in the direction of development. From February 1, 2015, the state began to impose a 4% consumption tax on coatings, but the VOC content≤ of 420 g/L in the construction state of coatings, can be exempted from consumption tax. GB/T 35602-2017 "Green Product Evaluation Coatings", "Low Volatile Organic Compound Content Coatings Product Technical Requirements" and other standards and specifications are also being prepared and implemented.
then, solvent-free thick-film epoxy coatings were introduced, not only to meet and pass different multi-regional standards (AS/NZS 3750.2, CFE, NORSOK system 7B), its outstanding performance far exceeds the world's recognized standard requirements. By