Test you: What is bottom paint? What are the requirements for bottom coatings in their surrounding environment?

This post was last edited by JFTANG726 on 2010-1-29 at 16:48. The answer provided by this site is: Bottom paint is a type of coating that is applied to the bottom of a ship, below the light load waterline, in areas that are constantly submerged under water. The bottom coating consists of two types of coatings with different functions: the bottom anti-rust coating and the bottom anti-fouling coating. The bottom anti-rust coating serves as the underlying layer for the anti-fouling coating; it is applied directly to the steel surface or used as an intermediate layer, and it prevents rusting of the steel as well as corrosion of the steel by the toxic inorganic substances contained in the anti-fouling coating. The function of the bottom anti-fouling coating is to prevent marine microorganisms from adhering to the ship’s bottom, thereby maintaining its smoothness and cleanliness over a certain period of time, which helps to increase speed and save fuel. The environment and requirements for the hull coating are as follows. ①The primer is applied directly to the ship’s bottom steel plates; it must provide good rust prevention, as well as a strong adhesion to both the metal surface and the subsequent coatings (rust-proof coatings and anti-fouling coatings). ②Anti-rust paint is an intermediate coating applied over the primer and under the anti-fouling paint; its main requirement is to be water-impermeable. It is also necessary for the coating to have anti-rust properties and a certain level of adhesion, with the gloss of the coating not being too high. ③The anti-fouling coating is applied on top of the anti-rust coating on the ship’s bottom; it comes into direct contact with seawater to prevent marine organisms from attaching. In addition to strong anti-fouling properties and long-lasting efficacy, it is also required to have a tough coating that can withstand mechanical stress and water flow, good adhesion, and a smooth surface in order to reduce sailing resistance.

This post was last edited by JFTANG726 on 2010-1-29 at 16:48. Bottom paint is a type of coating applied to the bottom of a ship, below the light load waterline, in areas that remain submerged under water for extended periods. The bottom paint consists of two types of coatings with different properties: a bottom anti-rust paint and a bottom anti-fouling paint. Bottom anti-rust paint is the base coating for anti-fouling paint. Applied directly to the steel plates or used as an intermediate layer, it prevents rusting of the steel plates and stops the corrosive effects of the inorganic toxic substances contained in the anti-fouling paint. The function of bottom anti-fouling paint is to prevent marine microorganisms from attaching to the ship’s bottom, thereby maintaining its smoothness and cleanliness for a certain period of time – which helps to increase speed and save fuel. 　　(1) Since the hull of a ship cannot be maintained or repaired while it is in operation, repairs must be carried out when the ship is in dry dock or at a repair facility; therefore, it is necessary for the hull coating to have a lifespan as long as possible, within the limits permitted by economic and technical considerations, in order to improve economic efficiency and reduce costs associated with repairs and maintenance. Currently, countries widely use long-lasting bottom anti-rust paints with a service life of over 5 years, some even reaching 10 years; at the same time, self-polishing bottom anti-fouling paints are used, and the effective lifespan of such anti-fouling paints is generally designed to be less than 3 years. In this way, as the ship sails, the anti-fouling paint continuously releases toxic substances and dissolves. During regular maintenance of the ship, it is sufficient to use high-pressure water to remove any remaining anti-fouling paint as well as a small amount of marine organisms attached to it. Since the rust-proof paint remains intact, it is only necessary to apply anti-fouling paint again, which helps to **reduce maintenance costs and time required. Developed countries such as the United States have underwater scrapers that can remove marine organisms from large ships and auxiliary vessels directly underwater, thereby extending the effectiveness of their anti-fouling measures. The use of long-lasting anti-corrosion primers and non-iron fouling paints on the hull is a trend in hull coating development. 　　(2) The bottom coat of the ship can be applied by methods such as high-pressure airless spraying, manual brushing, or roller coating. Specific coating application techniques and methods are described in Chapter 3 of this book. For high-solid rust-inhibiting primers, a high film thickness can be achieved in a single application using high-pressure airless spraying; however, edges and corners such as welds and rivets should first be coated manually. The secondary derusting of the hull steel should generally reach the Sa2.5 grade; after removing oil and dust, a well-mixed coating is applied. The coating should be applied in strict accordance with the design specifications, and a certain dry film thickness must be achieved to ensure long-term corrosion resistance. To improve the interlayer adhesion of rust-proof and anti-fouling paints, an intermediate coating is usually applied. When applying each coat of paint, pay attention to the drying time of the paint as well as the minimum and maximum time intervals between applications. 　　(3) Bottom anti-fouling paint is generally single-component, but due to the high content of toxic substances in it, precipitation often occurs. An appropriate amount of anti-settling agents, such as organic bentonite and aluminum stearate, can be added to the paint formula. Before application, the paint must be thoroughly mixed evenly. Rosin reacts with cuprous oxide to form copper rosinate; therefore, attention should be paid to the storage period of the coating, which generally should not exceed one year. 　　(4) The anti-fouling paint should work well in combination with an anti-rust primer; contact-type anti-fouling paints require a primer with strong anti-rust properties, such as an epoxy-asphalt system. Pay attention to the painting interval: it is 24 hours per ship, with a minimum of 14 hours and a maximum of no more than 10 days. 　　(5) Antifouling paint can be applied by high-pressure airless spraying, or by manual brushing or rolling. High-pressure airless spraying not only offers high efficiency but also enables the achievement of a thicker coating layer. Generally, no diluent is added or only a small amount is used to avoid affecting the anti-fouling effect. The film thickness of the anti-fouling paint must be strictly checked to ensure it reaches a certain thickness. Antifouling paint must not be applied directly on bare steel plates or inside compartments. 　　(6) Toxicants are highly toxic; in particular, organotin compounds are volatile and can affect the development and survival of other non-target organisms. As a result, many developed countries have imposed strict restrictions on the amount of organotin in anti-fouling paints. During painting, proper personal protective equipment must be used, and direct contact with the paint by hand is strictly prohibited. A mask should be worn when applying or removing old paint, and if symptoms such as headache occur during the work, one should leave the site immediately. If anti-fouling paint gets on the skin, it should be wiped off immediately and then washed with soap. 　　(7) When painting aluminum-hulled ships, antifouling paints based on acrylics with organotin as a preservative are commonly used. Do not use anti-fouling paints based on copper-mercury compounds, as these non-ferrous metals are highly corrosive to aluminum alloys. Wooden ships generally use antifouling paint based on rosin, copper soap, and coal tar pitch, containing the toxic substance cuprous oxide. Copper compounds are effective poisons to prevent shipworms. 　　(8) For large ships, bottom cleaning can be employed; using an underwater scraper at the initial stage of marine biofouling accumulation yields good results and can extend the service life of the anti-fouling paint. Generally, after a ship is launched, its speed can be restored by cleaning it every 3 to 6 months over a period of 1 to 1.5 years. 　　(9) For antifouling paints containing asphalt, prolonged exposure to sunlight and alternating wet and dry conditions can cause defects such as cracking and crazing in the paint film. To achieve the best anti-fouling effect, the vessel should be put into service within 40 days after applying the anti-fouling paint (if more time passes, it should be regularly watered for maintenance); ideally, it should be put into service 1–2 days after applying the final coat of anti-fouling paint.

This post was last edited by JFTANG726 on 2010-1-29 at 16:49. The most common method to prevent marine organisms from attaching to the bottom of a ship is to apply paint to that area. The anti-rust paint in ship coatings consists of two main components: bottom anti-rust paint and marine anti-rust paint. Bottom anti-rust paint is a specialized anti-rust coating used to protect the steel plates on the ship’s bottom when the coating layer is submerged in water for extended periods of time. It should possess the following properties: ① The coating layer must have excellent adhesion to the steel surface in wet conditions, and it must not bubble or peel off under the effects of prolonged immersion in water and water flow ； ②The paint film has good water resistance, with low water permeability and oxygen permeability ； ③Good drying performance ； ④It has good compatibility with bottom anti-fouling paints, exhibits strong interlayer adhesion to the paint film, and does not interfere with the anti-fouling properties of the paint ； ⑤The paint film exhibits good alkali resistance and potential resistance, and can be used in conjunction with cathodic protection systems. GB 13351-92 specifies the following technical requirements for anti-rust paint on ship bottoms. The standalone bottom anti-rust primer shall meet the following technical specifications: Parameter, Specification – Drying time, surface dry time, in hours: as specified by the product’s technical requirements; full dry time, in hours: ≤24. Adhesion, on a scale of 1 to 5: ≤2. Saltwater resistance: after 24 days in saltwater, the paint film shall not peel off, and the allowable area of rusting is limited to 5%. A complete bottom anti-rust paint system shall meet the following technical specifications: Parameter, Specification – Drying time, surface dry time, in hours: as specified by the product’s technical requirements; full dry time, in hours: ≤24. Adhesion, in Pascals: ≤1.96×105 for asphalt-based paints, and ≤2.94×104 for other types of paints. Saltwater resistance: after 30 months in saltwater (grade 1), or after 18 months in saltwater (grade 2), the paint film shall not peel off, with the allowable area of rusting limited to 5%. After 12 months in saltwater (grade 3). Note ； The thickness of the paint film should meet the product’s technical requirements.

This post was last edited by JFTANG726 on 2010-1-29 at 16:49. Bottom paint is a type of coating applied to the bottom of a ship, which is submerged underwater below the ship’s light load waterline, over a long period of time. The bottom coating consists of two types of coatings with different functions: the bottom anti-rust coating and the bottom anti-fouling coating. The bottom anti-rust coating serves as the underlying layer for the anti-fouling coating; it is applied directly to the steel surface or used as an intermediate layer, and it prevents rusting of the steel as well as corrosion of the steel by the toxic inorganic substances contained in the anti-fouling coating. The function of the bottom anti-fouling coating is to prevent marine microorganisms from adhering to the ship’s bottom, thereby maintaining its smoothness and cleanliness over a certain period of time, which helps to increase speed and save fuel. The environment and requirements for the hull coating are as follows. 1. The primer is applied directly to the ship’s bottom steel plates; it must provide good rust protection and have a strong adhesion to both the metal surface and the subsequent coatings (rust-proof coatings and anti-fouling coatings). 2. The anti-rust coating is an intermediate layer applied over the primer and under the anti-fouling coating; its main requirement is to be water-impermeable. It is also necessary for the coating film to have anti-rust properties and a certain level of adhesion, with low gloss. 3. The anti-fouling coating is applied over the antirust coating on the ship’s bottom; it comes into direct contact with seawater to prevent marine organisms from attaching. In addition to strong anti-fouling properties and long-lasting efficacy, it is also required to have a tough coating that can withstand mechanical stress and water flow, good adhesion, and a smooth surface in order to reduce sailing resistance.

This post was last edited by mopeizhi on 2010-2-7 15:02. Bottom paint is a type of coating applied to the bottom of a ship, which is submerged underwater below the ship’s light load waterline, over a long period of time. The requirements in its operating environment are as follows: (1) Before painting, the pre-treatment of the steel plates must strictly meet the standards for secondary rust removal; oil and dirt should be removed, the surface wiped with solvents, and painting should be carried out as soon as possible to prevent the steel from oxidizing and rusting again. (2) Select appropriate types of coatings and corresponding solutions based on the different parts of the ship and its various usage requirements. Each coat of paint should be applied in accordance with the requirements specified in the product’s instruction manual. Before painting, verify that the type, color, specifications, and model of the paint being used meet the technical requirements for painting. Check the quality of the paint as well as its shelf life; paint that has exceeded its shelf life must be retested by a qualified testing facility before it can be used. (3) Diluents must be used as required, generally not exceeding 5% of the amount of paint used. Harmful solvents or pigments are not allowed to be added to the paint; it should be mixed evenly before use, and filtered according to the requirements of the painting method. For two-component coatings, the curing agent must be added in proportion and mixed thoroughly; there is a certain activation period, and it must be used up within that time frame. (4) The construction unit may adopt appropriate coating methods depending on the properties of the paint, the surface condition of the object to be coated, and the environmental conditions; common methods include brushing, rolling, air spraying, airless spraying, and scraping. To improve efficiency and achieve an aesthetically pleasing coating film, high-pressure airless spraying is generally used. However, for painting in small compartments, roller coating or manual brushing is still used. Pre-coat the flow holes, the back side of the angle iron, and areas that are difficult to spray using brushes, angled brushes, etc. The areas where different metals come into contact, as well as rivets, welds, and sharp edges, should be coated with paint first, before spraying. (5) The coating film should reach the specified dry film thickness; during the coating process, the wet film thickness is continuously measured to estimate how many coats are required to achieve the specified dry film thickness. Before applying the spray coating, a test spray should be carried out to select the appropriate nozzle and adjust the proper pressure. (6) When applying anti-rust coatings, it is best to use coatings of the same type but different colors for each layer, in order to prevent missed applications and to facilitate quality inspection. After painting is completed, the total dry film thickness must be checked in accordance with relevant standards, and a coating leak test must be conducted. (7) Painting is prohibited on surfaces that are not suitable for painting, such as sacrificial anodes, insoluble auxiliary anodes, reference electrodes, the receiver and transmitter threads of depth sounders, markings, rubber seals, valves, steel cables, and moving friction surfaces. When spraying or applying coating using other methods, cover it with tape. (8) It is strictly prohibited to apply anti-fouling paint or waterline paint directly onto exposed metal surfaces or interior walls of compartments. (9) Open-flame operations are strictly prohibited during segmented painting. High-pressure airless spraying requires strict adherence to operating procedures and prevention of environmental pollution caused by the spray. Install appropriate ventilation equipment to prevent the toxicity of solvent evaporation to human health and potential fires, while ensuring construction quality. When painting in confined spaces, artificial ventilation is necessary; the workers must wear gas masks, and the working period should not exceed half an hour at a time. (10) Painting work is generally carried out in an environment with a temperature of 5–30°C and a relative humidity below 85%. Painting should not be carried out outdoors when it is raining, foggy, or when the ship’s hull is covered with moisture, frost, or snow. Painting is also not advisable in conditions of strong winds and high dust levels. The temperature of the steel plate should be at least 3°C above the dew point, and the ambient temperature must not be lower than the minimum temperature specified for coating drying. (11) Special coatings, such as zinc yellow primers, should be used for aluminum, galvanized, or other specially treated surfaces; primers containing copper, mercury, or lead pigments are not permitted. (12) The welds and rivets on the hull section shall not be painted within 10 mm around them prior to the water tightness test ； Do not paint within 50 mm of the weld edge before welding. It should be covered with paper or plastic film during painting, and removed promptly after painting. (13) To ensure coating quality, the section can be moved only after the coating has fully dried. Avoid scratching or abrasion of the coating when moving. (14) Before applying the coating, the contractor shall estimate the amount of coating required based on factors such as the painting area of various parts of the ship, the method of application, the substrate, and previous construction data, and shall prepare a detailed construction plan.

This post was last edited by mopeizhi on 2010-2-7 15:03. Bottom coating: refers to the paint applied to the bottom of various ships to prevent the ship’s floor from corroding. Requirements for bottom coating: strong corrosion resistance ； Long service life ； Environmental protection ； Resistant to seawater corrosion ； It sticks firmly and does not easily fall off.

This post was last edited by mopeizhi on 2010-2-7 at 15:04. To prevent marine organisms from attaching to the bottom of a ship, the most common method is to apply coatings to that bottom. However, the bottom coatings currently in use all contain harmful compounds to varying degrees; these toxic substances contaminate water quality and pose threats to marine organisms such as fish. A Japanese company has developed a new type of conductive coating that contains no toxic substances and can effectively prevent marine organisms from attaching to it. The working principle of this new type of coating is as follows: A coating containing metal powder is applied to the bottom of the ship, serving as the anode, while other parts of the ship’s hull that come into contact with seawater act as the cathode. By applying a voltage between these two poles, a weak electric current flows through the coating – a current that cannot be felt even when in contact with the skin. This current enables the electrolysis of hydrogen ions and hydroxide ions in seawater into hypochlorite ions, thereby forming a 10-micron-thick film on the surface of the ship’s bottom, which prevents marine organisms from attaching to it. Since the concentration of hypochlorite ions near the bottom of the ship is much lower than that in tap water (hypochlorite being the main component of bleach), it does not pollute the seawater nor affect the growth of fish. Furthermore, hypochlorite ions that diffuse into seawater can naturally revert back to chloride ions and hydroxide ions, so there is no issue of an increasing accumulation of hypochlorite ions in seawater. Another major advantage of the new coating is that it does not dissolve in seawater, eliminating the need for regular repainting and providing long-lasting anti-adhesion properties.

This post was last edited by mopeizhi on 2010-2-7 at 15:05. Since seawater has high levels of chloride ions, high dissolved oxygen, and high electrical conductivity, all of which have a significant impact on corrosion, coatings must be able to adapt to such conditions.

This post was last edited by mopeizhi on 2010-2-7 15:06. Bottom anti-corrosion coating is a coating used to prevent corrosion at the bottom of a vessel. The coating can provide a longer protection period than conventional coatings. The bottom of a ship is constantly exposed to highly corrosive seawater, and it cannot be maintained regularly; therefore, the anti-rust paint on the ship’s bottom must have the ability to protect the steel plates from corrosion over the long term.

A special coating applied to the hull and underwater marine facilities; it is usually applied on top of the anti-rust paint on the hull, forming the outermost layer. Its main function is to gradually release toxic substances through mechanisms such as the seepage, diffusion, or hydrolysis of these substances within the paint film, thereby preventing marine fouling organisms from attaching to the hulls of ships or underwater marine structures. 　　China has a coastline of over 18,000 kilometers, and the breeding times, species, and populations of marine organisms vary across different sea areas; each harbor has its own species of fouling organisms. More than 18,000 species of organisms in the world’s marine regions are sessile animals, and more than 600 species are sessile plants. When marine organisms attach to the bottom of the ship, it increases resistance, reduces speed, raises fuel consumption, and accelerates mechanical wear. The attachment of marine organisms also damages the paint coating, accelerating the corrosion of the steel plates. This not only increases the frequency and duration of ship maintenance but also reduces the ship’s operational rate. For ships, marine life has a significant impact on speed; if it attaches itself to the sonar dome, it interferes with the sound detection capabilities, thereby reducing the combat effectiveness of the warship. 　　To date, applying anti-fouling paint to ships remains the most economical and effective measure to prevent the attachment of marine organisms; therefore, the bottom of ships needs to be coated with anti-fouling paint. 　　Antifouling coatings should possess the following properties: 1. They should be able to prevent the attachment of marine fouling organisms over a certain period of time ； 　　2. The toxic substances within the paint film gradually seep into the seawater in a steady manner ； 　　3. The paint film has a certain level of water permeability to ensure continuous leakage of toxins ； 　　4. It should have good adhesion and compatibility with rust-proof paint; the anti-fouling paint itself should also exhibit good interlayer adhesion and be able to dissolve slightly in the rust-proof paint. 　　5. The paint film must have good resistance to seawater impact, and must not bubble or peel off when submerged in water for long periods of time ； 　　6. During navigation, it possesses self-polishing capabilities to varying degrees ； 　　7. It has good storage stability, typically lasting for 1 year, with no decline in its anti-fouling properties during storage