Epoxy zinc-rich primer has a high zinc content, steel substrate has a good cathodic protection effect, rust resistance is very good, can be applied to medium or even severe corrosion environment, known as the foundation of the heavy anti-corrosion system supporting. In the structure of offshore oil platform, zinc-rich primer epoxy has been widely used. The structural construction process, coating hardware facilities and construction technology level of the offshore oil platform construction site all have a direct impact on the quality of the coating and the anti-corrosion effect
. Therefore, according to the construction process of offshore oil platform structure, take reasonable and feasible coating process, control all aspects of coating construction, in order to ensure the construction quality of epoxy zinc-rich primer, play its excellent anti-corrosion performance.
1, epoxy zinc-rich primer introduction
epoxy zinc-rich primer is epoxy resin as the base material, ultra-fine zinc powder as the main anti-rust pigment, polyamide resin as a curing agent, with the appropriate amount of thickeners, additives, fillers, mixed organic solvents and other components of the two-component package coating. Zinc powder content of up to 85% or more.
epoxy zinc-rich primer drying speed, in the metal surface has excellent adhesion, mainly used in heavy corrosion protection, can provide long-term protection for steel structures in a highly corrosive environment. Epoxy zinc-rich primer film tough, wear-resistant, strong impact resistance, temperature changes caused by small stress deformation. Under dry conditions, its maximum temperature of use is 140 degrees C, with certain anti-humidity, excellent salt spray, anti-aging and other anti-corrosion properties. Moreover, its conductivity is excellent, with good gas cutting, does not affect welding construction.
zinc-rich primer coating can be compatible with most two-component paints and is ideal for multi-coated matching systems. Suitable for ships, offshore steel structures, storage tanks, petrochemical plants, paper mills, bridges and power plants.
The corrosion-proofing of zinc-rich primers is based on the cathode protection of metal zinc on steel substrates in corrosive environments.
first of all, epoxy zinc-rich primer plays an electrochemical protection role. In the early stage of corrosion, because zinc is relatively active relative to iron, easy to lose electrons, zinc powder and steel substrates make up the original battery, zinc potence is lower than iron potence, so zinc in the paint film is anode, steel substrate is cathode, steel substrate has cathodic protection.
is the shielding protection of steel from zinc corrosive deposits. In the late stages of corrosion, the sacrificated zinc produces a priceless zinc ion that reacts with water and carbon dioxide in the surrounding environment, producing alkaline zinc carbonate, commonly known as "white rust". Its dense structure blocks and shields the erosion of corrosive media and is therefore also known as the self-healing effect of zinc-rich primers to protect steel substrates.
2, offshore oil platform epoxy zinc-rich primer typical coating matching
In the offshore industry, most of the current offshore oil platform structure used primers are epoxy zinc-rich primers. Anti-corrosion design documents generally require that the definition and performance requirements of zinc-rich epoxy primers should meet the requirements of SSPCPaint 20. The quality ratio of zinc powder content should reach 80% and above the solid content. Zinc powder purity should meet ASTM D 520 (TYPE II.) requirements. In summary, the three typical coating systems of the ocean platform structure are found in Table 1, Table 2 and Table 3.
System 1: Steel structures above the splash zone such as structural support beams, sub-deck surfaces, containers, valve sets, pipelines, pumps, railings, ladders and handrails, brackets, horse feet, light poles, process equipment pry seats and the outer surface of the structure (no insulation, operating temperature ≤120 degrees C). See table 1.
in the above 3 coating systems, workshop primers are selected, according to the specific construction process to choose to paint or not to paint, if not applied to the workshop primer, the total thickness of the coating can be reduced by 25mm. In coating system 3, if the steel wall surface needs to be insulated, the paint can be omitted.
three coating systems, covering most of the main structure, ancillary structure and equipment above the splash zone of the offshore oil platform. In addition, it is not suitable to coat the epoxy zinc-rich primer parts, generally: immersion zone, tide differential zone, splash zone, container interior, galvanized part, aluminum, copper and copper alloy and other non-ferrous metals, stainless steel (including two-way stainless steel) surface, pipeline interior, insulation equipment and pipelines, high temperature parts.
3, offshore oil platform structure construction process
due to the differences in construction concepts, but also mainly because of the construction site of the hardware facilities conditions, as well as the overall design progress of the project and materials in place, there are some differences in the platform structure construction process.
3.1 Traditional construction process
the traditional offshore oil platform construction, is based on the professional division of labor, according to the deck level piece from low to high layer-by-layer prefab, to be installed on each deck after the column ramp, wall leather, piping, HBT, machinery, electric instrument, installation and other professional installation, generally the main structure, then the subsidiary structure and other professional.
installation of the main structure, the prefabriced and installed subsidiary structure and subsequent professional parts will result in a large number of cutting, polishing, opening, welding and other work, inevitably causing damage to the completed deck paint. As a result, a lot of paint repair work is added.
3.2 Integrated construction process
Offshore oil platform integrated construction, is in the structural deck horizontal prefabricing completed in the pre- installation phase and pre-installation phase of the subsidiary structure, pipeline, machinery, electrical instrument, installation and other professional bracket, base installation, to achieve the overall coating.
after the deck piece prefab, the structure parts such as tube support, equipment base, electric instrument bracket, ventilation pipe support, etc. are installed on the deck piece. After the bulk installation is completed, the deck pieces are artificially blasted and coated.
coating of the deck pieces, they will be transported to the assembly site for installation of grilles, pipelines, bays, installable structural parts and some equipment. After the pre-installation, the deck pieces are lifted as a whole. After the deck is hoisted, the column ramp, the installation of the wall skin, and the welding installation work can be carried out only after the wall skin is completed.
With integrated construction, in the platform air construction phase, in addition to the necessary welding work such as columns, sloping support and wall skin, the welding work of the remaining accessories is greatly reduced, the damage to the finished paint can be reduced as much as possible, and the work of polishing and repairing the paint is also reduced.
3.3 Advantages of an integrated construction process
Theoretically, steel structures should complete welding work as far as possible before blasting and coating, minimizing the damage of subsequent welding operations to previous coatings and ensuring the integrity of the paint film, so that the coating can achieve the best anti-corrosion effect and obtain a longer anti-corrosion life. According to examples of offshore oil platforms over the years, rust often occurs from the weld position, especially after secondary welding and then polishing the parts of the repair paint. It is clear that an integrated construction programme with reasonable design and management in place can improve the overall construction efficiency while also improving the quality of the coating.
4, epoxy zinc-rich primer coating process
4.1 construction overview
is still using the traditional construction process of the site, mostly due to hardware facilities, the lack of a large structure can accommodate the entire platform deck piece and sand blasting and coating workshop, only in the open air deck film feeding, production and coating. In addition, there are follow-up professional design progress is relatively lagging, materials in place relatively late reasons.
open-air blasting, because of abrasive recovery difficulties and cost control reasons, will generally use copper ore as an abrasive. In order to ensure the progress and quality of the platform deck film blasting, before the deck plate production process, it is usually recommended to combine beams, H-type steel, structural angle steel, steel deck and other materials in the blast workshop for blasting rust removal, spray workshop primer, pre-treatment of the material before the material is lowered, group paired, welded. When the deck pieces are finished, they are surrounded in place around the deck, followed by artificial blasting of the deck pieces. Theoretically, the workshop primer can be retained, the weld position according to the SSPC-SP10 standard sand blasting, the rest of the workshop primer can be in accordance with the SSPC-SP7 grade sand sweep, sand blasting and then sprayed epoxy zinc-rich primer. However, open-air production is usually the workshop primer damage and pollution is more serious, so it is generally required that all parts of the deck piece are in accordance with the SSPC-SP10 standard sand blasting, sand blasting, cleaning after the overall spraying of epoxy zinc-rich primer.
After the deck is hoisted, the subsequent installation of the column, oblique support, wall skin and other ancillary structure lines and pipelines, electrical instrument, machinery, installation and other professional brackets, base, etc., before installation, the manufactured parts or steel raw materials in accordance with the SSPC-SP10 standard rust removal, and then sprayed with zinc-rich paint.
use of integrated platform deck pieces, used to make deck profiles and plates without pre-treatment, directly under the group production can be. Deck prefab made, to be pre-installed , the deck piece will be moved into the blasting workshop, using steel balls and other abrasives, according to the SSPC-SP10 standard for the overall blasting. After the blasting is complete, the whole epoxy zinc-rich primer is sprayed.
deck piece after spraying epoxy zinc-rich primer, on the ground to complete the paint, finish the coating, and then lift. After the installation of deck pieces, columns, ramps, wall skins and other ancillary structures and other professional components of the subsequent production, installation of welds, inlets, need to use power tools in accordance with SSPC-SP11 standards for processing, treatment of standards, and then epoxy-rich zinc primer repair, as well as the subsequent medium paint, finish coating.
4.2 Construction technical points
(1) Steel surface treatment
steel structure surface treatment, all possible adverse surface defects of the protective paint system must be treated, all lacquer structure, fur edges, solder slag, oxidation skin, jagged objects and other sharp surface protrusions must be removed, sharp edge corners and welds need to be polished smooth.
surface of steel should be cleaned, should be kept dry, clean and pollution-free, oil and grease should be in accordance with SSPC-SP1 provisions for solvent cleaning.
blast rating is SSPC-SP10. After sand blasting treatment of the surface, in the case of rust before coating, the surface should be reseeded to the prescribed visual standards.
surface roughness after sand blasting should be between 50 and 85 m. Dust, abrasives, etc. retained on the surface after sand blasting should be removed and the number and size of particles retained should not exceed level 2 as specified by ISO 8502-3.
the maximum content of soluble salts on the surface after sand blasting should meet the requirements of ISO8502-6, the conductivity measurement should meet the requirements of ISO 8502-9 and the NaCl content of ≤50 mg/m2.
and paint damage caused by subsequent construction on the platform should be cleaned according to SSPC-SP11 standards to avoid polishing the substrate, while ensuring a certain degree of surface roughness.
(2) coating link
when coating construction, the relative humidity should be <85%, the surface temperature of the substrate is higher than the dew point of more than 3 degrees C.
primer is a two-part coating, each time must be matched according to the regulations. After stirring the base material, add the curing agent, stir thoroughly so that the two parts are fully and evenly mixed, according to the situation to add a moderate amount of thinner. After mixing, the primer should be used up for the life of the mixture.
spray method is recommended. Before spraying, edges, corners, welds, small brackets, etc. should be pre-coated. Brushing and rolling are only used for small-scale patching.
(3) Before re-painting spraying, edges, corners, welds, small brackets before coating, edges, corners, welds, small bracket links
In the event of widespread damage and contamination of the zinc silicate workshop primer, sand blasting should be carried out.
after the epoxy zinc-rich primer has been coated and dried, it is recommended that the coating of medium and finish paint be completed continuously as soon as possible. Some platform construction projects for the integrity of the paint film, the main structure of the platform only do primer, to be attached structure and other professional construction welding installation completed, repair primer, before the paint, paint coating. If the re-painting interval is longer, the zinc salt on the surface of the epoxy-rich primer should be removed and thoroughly pulled before construction. If you have experienced salty mist by the sea, fresh water should be used for cleaning before construction.
zinc-rich primer has excellent anti-corrosion properties and is widely used in offshore oil platform structure. In the construction process, the builder should combine the construction process of offshore oil platform structure, adopt reasonable and feasible coating process, follow the relevant norms and standards, and control every aspect of coating construction. In this way, we can ensure that the quality of epoxy zinc-rich primer and its supporting coating system meet the requirements and provide excellent corrosion protection for offshore oil platform.