Application of Environmental Protection Coatings in the Anticorrosion of Offshore Oil Facilities

0 Preface

Offshore oil platforms, jackets, submarine pipelines and other oilfield facilities have complex structures, harsh corrosive environments and difficult maintenance.

1 Water-based paint

Water-based coatings are coatings that use water as a solvent or water as a dispersion medium to meet the environmental requirements for VOC emissions.

Water-based coatings have broad application prospects as workshop primers

2 Solvent-free paint

Solvent-free coatings are also called active solvent coatings.

The solvent-free epoxy resin system can also be directly applied to the surface of the substrate with low surface treatment, such as high-pressure water jet, manual or mechanical tool cleaning, etc.

Polyurea coating is a type of compound formed by the reaction of isocyanate component and amino compound.

However, solvent-free coatings have a fast curing and crosslinking speed and a short pot life after two-component mixing.

3 High solids coating

Generally, non-volatile matter volume fraction> 70% is defined as high solids coatings, and non-volatile matter volume fraction> 85% is defined as ultra-high solids coatings
.
The VOC of high-solid coatings is less than 250 g/L, which meets the requirements of GB/T 35602-2017 for green products
.
High-solid coatings have many of the same advantages as solvent-free coatings.
For example, a single coating completed at a time can achieve long-term anti-corrosion effects, excellent seawater resistance, and can be directly applied to the surface of low-surface treatment substrates.
curing may continue under submerged environment
.

The splash zone of the ocean is impacted by rising and falling tides and waves, and the impact and erosion of floating objects on the sea surface are the most severely corroded areas
.
In the Bohai Sea region of China, where the winter temperature is low, a large amount of sea ice will be formed, and the wear resistance and impact resistance of the splash zone coating will be higher
.
Epoxy-based high-solid coatings also generally have high abrasion resistance, impact resistance and strong adhesion properties.
After some products are strengthened with glass flakes, they have stronger impact resistance.
It is currently the structure of jackets and other services in the splash zone.
The most widely used paint product
.

High-solid paint contains a certain amount of organic solvent, its viscosity is greatly lower than solvent-free paint, and the difficulty of construction is greatly reduced compared with solvent-free paint.
It can be applied with ordinary one-component paint spraying machine, but the pressure during construction is higher than that of ordinary paint
.
High-solid coatings are more suitable for spraying with a two-component sprayer.
The use of a two-component sprayer reduces the amount of thinner in the painting process, and reduces the amount of equipment cleaning solvents caused by the interruption of painting, and further reduces VOC emissions
.
High-solid coatings not only meet the requirements of environmental protection, the construction is relatively convenient, and it also has a better cost advantage than solvent-free coatings
.
This will be the development direction of green coating in long-term anticorrosion of offshore oil facilities
.

4 Powder coating

Powder coating is an organic polymer coating, which is composed of solid resin, pigments, fillers and additives
.
It is applied as a free-flowing dry powder during application and then cured under heating
.
Compared with the traditional liquid coating, the powder coating system does not require a solvent to keep the binder and filler in a liquid suspension.
Its dispersion medium is air, which has the advantages of no solvent pollution and 100% film formation
.
The most commonly used polymers are polyester, polyurethane, polyester epoxy resin, fusion bonded epoxy resin, and acrylic resin
.

Fused epoxy coating has good solvent resistance, can resist the chemical corrosion of hydrogen sulfide, acid, alkali, organic matter and other substances, and can resist the corrosion of various organic acids and other substances produced by microorganisms in seawater and soil for a long time; The layer has good insulation and strong cathodic stripping resistance, and can be used in conjunction with cathodic protection to achieve the purpose of long-term protection
.
Therefore, fusion-bonded epoxy resin coatings are widely used in the anti-corrosion of oil well pipes and submarine oil pipelines
.
Fused epoxy resin coating is a kind of thermosetting coating.
The pipeline is sandblasted and heated at medium frequency before spraying, and then the epoxy powder coating is sprayed on the surface of the heated steel pipe by electrostatic spraying, and then melted and bonded to the surface of the steel pipe.
Form a coating
.
The anti-corrosion inside the tubing often uses a single-layer fusion-bonded epoxy coating, and the outside of the pipeline uses a fusion-bonded epoxy coating plus three layers of polyethylene heat-shrinkable tape or three-layer polypropylene heat-shrinkable tape
.

The powder coating needs to heat and rotate the construction work during the construction process, and the spray room, heating room, etc.
are required during the construction.
The coating is only suitable for assembly line construction in the workshop, and cannot be carried out on a large scale outside the workshop, and it is not suitable for the structure.
The construction of complex components is mainly used for pipeline anti-corrosion
.

5 Bio-based coatings

Epoxy resins, alkyd resins, polyurethanes, phenolic resins, acrylic resins, polyesters, etc.
are all petroleum-based polymers, whose synthesis and application process emit volatile organic compounds, which can pollute the environment and endanger human health
.
Therefore, people are looking for and exploring other green and renewable source polymer resins to reduce their dependence on fossil or petroleum-based materials
.
The use of bio-based materials to synthesize polymers/resins is one of the possible ways to solve these challenges
.
These bio-based materials are derived from nature, thereby helping to achieve global sustainability without consuming scarce resources
.
Using bio-based materials, including starch, lignin, protein, cellulose, sucrose, sugar, chitosan, shellac, rosin, polyhydroxyalkanoate, furanone, sodium alginate, wool fiber, vegetable oil and animal oil, etc.
, As a coating additive and modifier, it is used in various applications such as resin synthesis, adhesives, coatings, and composite materials
.

Cardanol is refined from natural cashew nut shell liquid through advanced technology.
It can replace or partially replace phenol in the manufacture of epoxy curing agents, liquid phenolic resins, liquid or powdered thermosetting phenolic resins.
Cardanol has its special Its chemical structure also has the following characteristics: (1) Containing benzene ring structure, with high temperature resistance; (2) Polar hydroxyl can provide the system to wet and active the contact surface; (3) Meta-position contains unsaturated double bond The carbon 15 straight chain can provide the system with good toughness, excellent water repellency, low permeability and self-drying
.
At present, cardanol has been widely used in the coating industry, especially for its good self-drying properties.
The modification of cardanol with epoxy resin curing agent can make epoxy coatings cure at a lower temperature
.
The fast-drying paint of cardanol modified curing agent is widely used in the winter paint used in the offshore oil industry
.

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