Application method for applying polyurethane fiber paint to corrosion prevention of ship shell outer plate on large scale

Abstract

The invention belongs to the technical field of corrosion prevention of ship and ocean engineering outer plates, and discloses a use method for applying polyurethane fiber paint to corrosion prevention of ship shell outer plates on a large scale. The paint solves the problem that a paint scheme for corrosion prevention of the outer plate of the ship shell, which combines long-period non-dock repair, old base layer adaptation and high-latitude environment tolerance, lacks in the prior art. Comprising the following steps: carrying out comprehensive rust removal and surface cleaning on an original outer plate of a ship, and carrying out repair welding and polishing leveling on a local damaged part; polyurethane fiber paint is constructed in a high-pressure airless spraying mode, the thickness of a dry film per degree is controlled to be 500 micrometers, and the total thickness of the dry film reaches 1000 micrometers at the temperature of 2 degrees or 1500 micrometers at the temperature of 3 degrees; and within 72 hours after construction is completed, the film thickness is detected, and the intact state of the coating is recorded. The anti-corrosion period can be prolonged, the method is suitable for old ship transformation and severe operation environment, and construction and detection are convenient and fast.

Description

Technical Field

[0001] This invention belongs to the field of corrosion protection technology for ship and marine engineering outer plates, and particularly relates to a method for the large-scale application of polyurethane fiber paint for corrosion protection of ship hull outer plates. Background Technology

[0002] In the field of ship conversion and marine engineering outer plate protection, corrosion prevention is a core requirement to ensure the long-term safe operation of equipment. Especially for the conversion of old ships and floating marine engineering (such as floating natural gas storage devices), the outer plate needs to withstand complex working conditions such as seawater immersion, salt spray erosion, temperature changes (such as the low temperature environment of high latitude ports), and ship vibration and impact. The corrosion prevention cycle directly affects the project operation and maintenance costs and operational safety.

[0003] At present, the anti-corrosion paints for the outer plates of ships and marine engineering are mainly divided into three categories: conventional epoxy paint, chlorinated rubber paint and traditional polyurethane paint. (1) Conventional epoxy paint: The anti-corrosion cycle is relatively short (usually 5-8 years), and the low-temperature curing performance is poor. The coating is prone to cracking in environments below -10℃, which is difficult to adapt to the operation requirements of high-latitude ports. (2) Chlorinated rubber paint: The weather resistance is relatively weak. It is easy to chalk and lose gloss when exposed to ultraviolet radiation for a long time. It needs to be recoated and maintained after 2-3 years, which cannot meet the long-term anti-corrosion requirements of more than 10 years. (3) Traditional polyurethane paint: Although the weather resistance and corrosion resistance are better than the first two categories, the conventional dry film thickness is mostly controlled at 100-150μm. The thick coating performance is insufficient (more than 200μm is prone to sagging and bubble defects). Moreover, it has not formed a suitable construction process for the uneven base layer and rust residue risk of the outer plates of 40-year-old ships, which is difficult to support the high requirement of not docking for 25 years. In addition, existing painting solutions are mostly for small areas (single ship outer plating area ≤ 5000m²). 2 This applies to ordinary cargo ships, but does not specifically address the retrofitting of two LNG carriers (total outer plating area ≥ 20,000 m²). 2 Large-scale scene design and construction processes are prone to problems such as poor coating uniformity (film thickness deviation of more than ±30μm) and local missed coating, resulting in uneven coating protection performance.

[0004] In the field of retrofitting old LNG carriers, especially 40-year-old vessels with MOSS tanks, the outer plates have problems such as base oxidation, local damage, and uneven surface roughness after long-term service. Existing painting solutions mostly focus on the "short-term protection + periodic docking repair" model, and lack technical solutions that combine "long-term non-docking repair + adaptation to old base plates + tolerance to high-latitude environments". Therefore, they cannot meet the retrofitting needs of floating natural gas storage units (long operating cycle and high docking repair costs). Summary of the Invention

[0005] The purpose of this invention is to provide a method for the large-scale application of polyurethane fiber paint for corrosion protection of ship hull plating, effectively solving the problem of the lack of existing paint solutions for corrosion protection of ship hull plating that combine the three factors of "long-term non-dock repair + adaptation to old base layers + high-latitude environment tolerance".

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a method for the large-scale application of polyurethane fiber paint for corrosion protection of ship hull outer plates, including the following steps: S1, pre-treatment of outer plates: the original outer plates of the ship are thoroughly derusted and the surface is cleaned, and local damaged areas are repaired by welding and grinding to ensure that the outer plate base meets the requirements for paint application.

[0007] S2. Painting process: Polyurethane fiber paint is applied using high-pressure airless spraying. The dry film thickness is controlled at 500μm per grade, and the total dry film thickness reaches 1000μm for 2 grades or 1500μm for 3 grades.

[0008] S3. Post-construction inspection and maintenance: Within 72 hours after construction, use a wet film thickness gauge and a dry film thickness gauge to check the film thickness to ensure that it meets the design requirements; record the condition of the coating to ensure stable protective performance during the 25-year no-dock repair cycle.

[0009] Furthermore, in step S1, the rust removal must meet SA 2½ (ISO 8501-1) level or SSPC-SP 10 rust removal standard, or WJ-2 high-pressure water jet flash rust level LM level.

[0010] Furthermore, in step S1, oil and impurities are removed during surface cleaning, and the surface roughness is controlled to be 50-80μm.

[0011] Furthermore, in step S2, the interval between each spraying should be in accordance with the product instructions for polyurethane fiber paint. The construction environment should be controlled as follows: temperature 5-35℃, relative humidity ≤85%, and construction should be avoided in rainy or windy weather.

[0012] Compared with the prior art, the beneficial technical effects of the present invention are: (1) it significantly extends the anti-corrosion cycle of the outer hull plate: it can achieve 25 years without dock repair, greatly reduce the number of times the ship enters the dock for maintenance, and reduce the maintenance cost in the later stage of the project.

[0013] (2) Adapting to the needs of old ship renovation: For the base condition of the outer plate of a 40-year-old LNG ship, the problem of protecting the old outer plate is solved by perfecting the pretreatment and thick coating process. Moreover, the paint construction process is highly compatible and does not require large-scale adjustment of the existing construction equipment for the renovation project.

[0014] (3) Adaptable to harsh operating environment: Ecolock polyurethane fiber paint has excellent low temperature resistance, and its salt spray resistance and seawater immersion resistance meet the standards, which can resist the long-term corrosion of the outer panel in the marine environment.

[0015] (4) Convenient construction and testing: It can be constructed using conventional high-pressure airless spraying equipment, and the testing methods are mature (film thickness testing, electric spark leak detection), which facilitates on-site operation and quality control, and reduces construction difficulty and quality risks. Detailed Implementation

[0016] Example 1: This example addresses the need to convert two 40-year-old LNG carriers with MOSS tanks into floating natural gas storage marine engineering projects (operating in Canadian ports). The core issue is to solve the key problem of long-term corrosion protection of the hull plating while meeting the shipowner's requirement of no dry-docking for 25 years. Through screening, Ecolock brand polyurethane fiber paint was selected. Relying on its thick coating characteristics and weather resistance and resistance to marine environment corrosion, combined with the application method of polyurethane fiber paint for large-scale corrosion protection of hull plating provided by this invention, a complete hull plating protection technical solution is formed.

[0017] The polyurethane fiber paint used in this embodiment is applied on a large scale for corrosion protection of ship hull outer plates. The specific steps include: S1, Pre-treatment of outer plates: The original outer plates of the LNG ship are thoroughly derusted (to SA 2½ (ISO8501-1) level or SSPC-SP 10 rust removal standard, or WJ-2 high-pressure water jet flash rust level LM level), and the surface is cleaned (removing oil and impurities, and controlling the surface roughness to 75μm). For local damaged areas, welding is carried out and the surface is ground smooth to ensure that the outer plate base meets the requirements for paint application.

[0018] S2. Painting process: Ecolock polyurethane fiber paint is applied using high-pressure airless spraying. The dry film thickness per coat is controlled at 500μm, and the total dry film thickness reaches 1000μm for 2 coats or 1500μm for 3 coats (to meet the requirements of thick coating). The interval between each coat should be in accordance with the Ecolock polyurethane fiber paint product instructions. Environmental control during construction: temperature 5-35℃, relative humidity ≤85%, avoid construction in rainy or windy weather.

[0019] S3. Post-construction inspection and maintenance: Within 72 hours after construction, use a wet film thickness gauge and a dry film thickness gauge to check the film thickness to ensure that it meets the design requirements; record the condition of the coating to ensure stable protective performance during the 25-year no-dock repair cycle.

[0020] Ecolock polyurethane fiber paint contains high-molecular-weight polyurethane resin that forms a cross-linked structure with fiber reinforcement components. After curing, it forms a high-density, highly elastic thick coating that effectively isolates corrosive media such as seawater, salt spray, and oxygen from contact with the outer substrate. Simultaneously, its elastic properties buffer against vibrations and impacts from ship operation and the marine environment. This embodiment ensures the adhesion between the coating and the substrate through pretreatment, guarantees coating uniformity and integrity through a reasonable spraying process and film thickness control, and promptly identifies and mitigates coating defects through subsequent inspection, collectively ensuring a 25-year anti-corrosion effect without the need for docking repairs.

[0021] This embodiment marks the first large-scale application of Ecolock polyurethane fiber paint (approximately 43,000 square meters of outer plating for the retrofit of two LNG carriers) to the outer plating of a floating natural gas storage unit on a 40-year-old MOSS tank-type LNG carrier. This breakthrough overcomes the limitations of traditional paints in the retrofitting of older vessels and long-term corrosion protection scenarios. It establishes an integrated technical solution for outer plating protection encompassing "pre-treatment - painting application - post-inspection," adaptable to the low-temperature, high-salt-spray marine environment of Canadian ports and meeting the requirement of 25 years without dry-docking. This solution deeply integrates the characteristics of thick-coat polyurethane fiber paint with the retrofitting process of older vessels, enhancing the targeted and stable protection of the outer plating.

[0022] This embodiment has the following advantages: (1) Significantly extended anti-corrosion period: Compared with traditional ship outer plate paint (conventional anti-corrosion period of 5-10 years), the Ecolock polyurethane fiber paint used in this embodiment can achieve 25 years without dock repair, greatly reducing the number of times the ship enters the dock for maintenance and reducing the operation and maintenance costs in the later stage of the project. (2) Adaptable to the needs of old ship renovation: For the base layer of the outer plate of a 40-year-old LNG ship, the problem of old outer plate protection is solved through perfect pretreatment and thick coating process, and the paint construction process has strong compatibility, without the need for large-scale adjustment of the existing construction equipment of the renovation project. (3) Adaptable to harsh operating environment: Ecolock polyurethane fiber paint has excellent low temperature resistance (can withstand the low temperature environment of Canadian ports in winter), and its salt spray resistance and seawater immersion resistance meet the standards, which can resist the long-term corrosion of the outer plate by the marine environment and ensure the safe operation of the floating natural gas storage device. (4) Convenient construction and inspection: It can be constructed using conventional high-pressure airless spraying equipment, and the inspection methods are mature (film thickness detection, electric spark leak detection), which facilitates on-site operation and quality control, and reduces construction difficulty and quality risk.

[0023] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A method for the large-scale application of polyurethane fiber paint for corrosion protection of ship hull plating, characterized in that: Includes the following steps: S1. Pre-treatment of outer plates: Thoroughly remove rust and clean the surface of the ship's original outer plates, and repair and grind the damaged areas to ensure that the outer plate base meets the requirements for painting. S2. Painting process: Polyurethane fiber paint is applied by high-pressure airless spraying. The dry film thickness per grade is controlled at 500μm, and the total dry film thickness reaches 1000μm for 2 grades or 1500μm for 3 grades. S3. Post-construction inspection and maintenance: Within 72 hours after construction, use a wet film thickness gauge and a dry film thickness gauge to check the film thickness to ensure that it meets the design requirements; record the condition of the coating to ensure stable protective performance during the 25-year no-dock repair cycle.

2. The method for applying polyurethane fiber paint according to claim 1 to large-scale corrosion protection of ship hull outer plating, characterized in that, In step S1, the rust removal must meet SA 2½ (ISO 8501-1) level or SSPC-SP 10 rust removal standard, or WJ-2 high-pressure water jet flash rust level LM level.

3. The method for large-scale application of the polyurethane fiber paint according to claim 2 for corrosion protection of ship hull outer plating, characterized in that, In step S1, surface cleaning is required to remove oil and impurities, and the surface roughness is controlled to be 50-80μm.

4. The method for large-scale application of the polyurethane fiber paint according to claim 3 for corrosion protection of ship hull outer plating, characterized in that, In step S2, the interval between each spraying should be in accordance with the product instructions for polyurethane fiber paint. The construction environment should be controlled as follows: temperature 5-35℃, relative humidity ≤85%, and construction should be avoided in rainy or windy weather.