Choice of marine coatings and coatings

Introduction:
is a very important part of the ship's coating, and the most important thing before coating is to choose a reasonable coating, so that it can meet the ship's coating requirements. Therefore, in the ship coating design, designers should choose the best coating according to the specific coating site, as well as the characteristics and requirements of the use of the site, to ensure the quality of ship coating.
1, different parts of the ship paint varieties to choose
each part of the ship contact with different corrosion media, the environment of contact is different, so different parts of the degree of corrosion will

. Therefore, in the selection of paint varieties, according to the actual situation of each part, the paint varieties to make a scientific and reasonable choice.
1.1 workshop primer selection
during the construction of the ship, corrosion problems may occur, workshop primers should be able to solve this problem. Smoke is generated during welding treatment, which can affect human health, and the primer of choice also solves this problem. At the same time, the workshop primer should be able to reduce the damage to the paint film, can be matched with the next coating, and the rust removal performance of the workshop primer should also be able to match the ship's construction cycle.
1.2 boat primer selection
this part should be selected rust resistance is better paint, it should have good adhesion, flexibility is good, but also have better electrical resistance. Anti-fouling paint film surface has a certain permeability, in the ship berthing, can also seep out of the poison. In addition, anti-rust and anti-fouling paint should be able to dissolve each other. There are several main types of anti-rust and anti-fouling paint coatings suitable for the bottom of the ship: (1) asphalt series; In addition, (since) polishing anti-fouling paint also has a wide range of applications.
1.3 Waterline coatings
the waterline is between ballest and full-load lines, and this area is vulnerable to multiple erosions. such as sea erosion, ocean atmosphere erosion, and daylight erosion. Moreover, the waterline is often hit by waves and is prone to mechanical damage, so the waterline is the most corrosive part of the ship. Therefore, this part of the coating should have good resistance to dry and wet alternating performance, with strong adhesion, can withstand friction and collision. More commonly used phenolic acid coatings, chlorinated rubber coatings, epoxy coatings and anti-fouling coatings.
1.4 Choice of Hull Coatings
The hull is located above the fully loaded waterline, and this part of the coating should have good weather resistance and good water resistance. Paint film to be more beautiful, with bright colors, but also have a better strength. Therefore, suitable for the hull of the paint has oil-based coatings, epoxy coatings, phenolic alcoholic acid coatings and acrylic anti-rust paint.
1.5 deck and water tank coatings
the coatings used in the decks should have good wear resistance, weather resistance and impact resistance. Phenol system, alcohol acid system, inorganic zinc system and other anti-rust anti-slip paint, are more suitable as deck paint. The water tank is usually corroded because it is not easy to enter the tank and repair it. If seawater ballast is used, the working conditions will be close to the working conditions of the bottom of the ship, so the rust-proof paint applicable to the bottom of the ship can be used for in-cabin coatings. If the cabin is ballast with drinking water and fresh water, the coating must have good rust removal properties and must not contaminate drinking water. Therefore, solvent-free epoxy coatings, cold-cured epoxy coatings, etc. can be used.
2, scientific and reasonable choice of paint film thickness
2.1 paint film minimum thickness
after pre-treatment of steel, the surface roughness will generally be between 40 to 75 m. In order to make the thickness of the paint film to meet the rust-proof requirements, then its thickness should be controlled between 100 to 150 m. Therefore, the minimum thickness of the paint film should be controlled between 140 and 195 m.
2.2 single-coated paint film thickness
in each coating coated by a ship, there is a critical thickness value, which is affected by a number of factors. For example, the nature and dosing of solvents, the properties of film coatings, surface treatment, etc. The greater the thickness of the single coating, the better the coating effect and the reduction in the number of coating lanes, thereby reducing the coating time. However, if the thickness is too large, the paint film will increase the internal stress, reduce the thickness of the film, but also affect the adhesion of the film. Therefore, in the selection of coating protection coating, to determine the thickness of a good paint film, it should have a smaller internal stress and strong adhesion, and has a higher strength.
2.3 Determination of the total thickness of the lacquer film
When confirming the total thickness of the lacquer film, the following factors should be taken into account: (1) the interval required by the shipowner; Typically, the total thickness of the paint film is the sum of the thickness of the single coating of each coating.
3, the determination of the number of coating channels and the matching of the ship's coating
3.1 the determination of the number of coating channels
coating in the hull to play a protective role, with the help of the dense characteristics of the paint film, it can block the erosion of sea water on steel. After the lacquer film is cured, a three-dimensional mesh structure is formed, which can block the sea water to a certain extent. However, a single coating creates a pinhole after the paint film is dry, so multiple coatings are required. In the process of multi-channel coating, the pinhole of the last lacquer film can be filled by the next coating, which can reduce the permeability of the membrane, thereby enhancing its rust resistance and adhesion. For example, the coating of the bottom of > should be 4 to 5, and the coating of the upper building should be at least 3 to 4. Only a small number of cabins can be painted only two: one for primer, one for finish.
3.2 Ship coating matching
In the selection of coatings, pay attention to the matching between the coatings, so that the upper coating and the lower coating can be bonded better. If the two layers can not be well matched, paint film may appear curing phenomenon, there will be a large area of paint film cracking, differentiation and other conditions, may also foam. The upper and lower layers of the binding force is not good, but also caused a large area of paint film off. For example, when the primer is asphalt system, can not be coated on top of the oil-based paint, asphalt system contains phenolic compounds, which will have an adverse effect on the drying of oil. Moreover, asphalt can dissolve in the paint coating, so that the color of the paint film changes. Therefore, when choosing the variety of coatings, we should consider the matching between the coatings.
4, calculate the actual amount of paint
4.1 calculate the amount of paint
in the actual coating process, the amount of paint should be accurately calculated. In the calculation process, the amount of paint used is expressed by the amount of paint required per unit area when applying a paint. In the actual coating process, it is inevitable that some coatings will be lost, but the amount of loss is usually in a state of change, so the approximation can only be calculated by approximate method, the calculated amount is also approximate. The actual amount of paint can be calculated using the formula P-KngS. Where K is a factor, the value of which depends on the coating method. Typically, when hand-painted, the value of K is taken from 1.2 to 1.3, the value of K is 1.4 to 1.8 when spraying, n is the number of coating channels, g is the theoretical amount of the unit area, can be found in the paint sample, in kg/m2, S is the coating area, unit is m2.
4.2 Calculate the area of
the total area of each part of the ship that needs to be coated. The surface shape of a ship is complex, so empirical formulas are often used to calculate the coating area. For example, the coating area of the bottom of the ship, one of the area below the light-duty waterline is calculated using formula S-S1-S2, where S1 represents the area below the heavy-duty waterline, and S2 represents the area between the light-heavy-duty waterlines. The area below the light-duty waterline in the other part is calculated using formula S .2TM.B.x Lpp x P. Among them, P is a coefficient, the cruise ship's P is 0.9, the bulk ship's P is 0.85, and the dry cargo ship's P is 0.7 to 0.75. The open-air deck contains a hatch and a first floor deck, and its area formula is S-L0 x B x N. Of these, N represents a coefficient of 0.92 for large tankers and bulk vessels, 0.88 for cargo ships and 0.84 for coastal cargo ships.
conclusion,
, with the changing natural environment, ships need to face more and more tests when sailing. Therefore, in the ship coating, according to the characteristics of various parts of the ship, working environment, scientific and reasonable choice of more adaptable coatings, in order to ensure the quality of coating. At the same time, we should choose the thickness of paint film, the number of coating channels, and the matching of marine coatings scientifically and rationally. In addition, the amount of paint to calculate, determine the actual need for the coating area, so as to achieve the best coating effect.