When repairing and maintaining the coating system, we need to know the type of paint originally used. How to judge the type of paint originally used? According to the coating drying mechanism, the commonly used coating types are divided into three types, oxygen curing type, physical drying type and chemical curing type. The three basic paint types can be distinguished using the MEK reagents. This method is suitable for rough testing on the application spot.
First, clean off the dust and oil on the surface of the old coating, then wipe the surface of the coating with a rag dipped in MEK reagent for 2-10 minutes, and observe the results:
(1) If the paint film is completely melted and wiped off, it would be chlorinated rubber, acrylic, vinyl, asphalt, or antifouling paint.
(2) If the paint film is greatly affected by the reagents, such as biting, wrinkling, etc., usually alkyd paint, modified alkyd paint or epoxy ester primer, etc., these are all oxygen-curable paints.
(3) If the paint film is not affected by the reagent, or has only a minimal effect, it is generally a chemically cured paint, such as epoxy paint, modified epoxy paint, and polyurethane paint.
(4) Asphalt is brown or black, and the paint film is soft and easy to distinguish.
(5) Antifouling paint is usually reddish-brown because of the addition of a large amount of cuprous oxide, which is easier to distinguish.
(6) If it is black or other colored paint, sometimes with some aluminum powder, the surface is with a slight blackening or yellowing and smells like bitumen, it may be epoxy coal pitch or polyurethane pitch paint.
(7) If the paint surface is zinc-gray and zinc powder can be scraped out, it is usually inorganic zinc silicate primer or epoxy zinc-rich paint, while the epoxy zinc-rich paint surface is more smooth.
(8) Epoxy paint will have a serious chalking phenomenon in an outdoor environment, and chlorinated rubber paint will also have this phenomenon when exposed for a long time.
In order to reduce the times of coating maintenance, the most commonly used heavy coating systems are as below:
Epoxy zinc-rich primer or inorganic zinc-rich primer 50-80μm
Epoxy mica intermediate paint 100-150μm
Acrylic polyurethane topcoat 2 x 40μm
The anti-corrosion coating system based on epoxy zinc-rich or inorganic zinc-rich primer has a dry film thickness of 200-320μm according to the different corrosive environment of the storage tank. The dry film thickness of epoxy zinc-rich primer is usually not less than 50μm. If an inorganic zinc-rich primer is used as an anti-rust primer, a sealant tie paint must be applied. The dry film thickness of traditional epoxy mica intermediate paint is usually 50-80μm, while the film thickness of Fuxi® high-solid epoxy mica intermediate paint can reach 150-200μm in one spray.
Fuxi® polysiloxane coating has outstanding weather resistance and can be applied with high film thickness. Which is allowing the traditional 3 to 4 coating system to reduce to two coating system, epoxy zinc-rich primer 75μm+polysiloxane 150μm, and the total film thickness can reach 225μm.
Wind power equipment is usually located more in a rural environment or coastal area, and less in an industrial environment. For the requirement of 15 years of serving life need less maintenance, the dry film thickness of the coating must reach 160-320μm. Fuxi® Paint has a good performance anti-corrosion protection coating system for wind power equipment.
The Tower tube is the main part that needs the care of anti-corrosion coating. Different coating systems are suitable for its inner and outer surfaces. The dry film thickness is set based on different climatic conditions.
The anti-rust primer on the exterior wall of the tower tube is mainly epoxy zinc-rich primer or inorganic zinc-rich primer, which can form a hard and wear-resistant coating. Zinc powder has a cathodic protective effect against corrosion caused by mechanical damage and also inhibits corrosion spreading. A better solution is to protect the steel surface by thermal spraying of metallic zinc. The intermediate paint is usually a thick coating type epoxy mica intermediate paint or modified epoxy thick build paint. The paint film is tough and resistant to seawater, forming a good shielding protective layer. The topcoat is made of polyurethane topcoat or acrylic polysiloxane topcoat with stronger gloss and color retention, which is resistant to ultraviolet rays, seawater, and salt spray. Another solution can also be applied with glass flake paint which paint film is super wear-resistant, and the topcoat is acrylic polyurethane paint to enhance the anti-corrosion performance and make it look good.
The paint on the interior tube of the tower tube should be epoxy zinc-rich paint and then coated with high-build epoxy paint. If heavy anticorrosive high-build epoxy paint is used, a zinc-rich primer could be saved.
The friction surface of the high-strength bolts between the tower tube sections is usually treated with inorganic zinc silicate primer for corrosion protection.
Wind turbine blades can be protected by polyurethane topcoat or polysiloxane topcoat.
New water-based heavy anti-corrosion coatings have also begun to be applied to the outer wall of the tower. Water-based epoxy zinc-rich primer/water-based epoxy intermediate paint/water-based acrylic topcoat matching system is wildly used, this coating system dries quickly and meets the construction requirements of a tight schedule.
The inner and outer walls of buried steel sewage pipes can be protected by the same coating system.
Below are the most widely used coating systems for sewage pipe inner and outer wall.
Option 1: Modified thick build epoxy coating 2 x 300μm
Option 2: Solvent-free epoxy glass flake 2 x 400μm
Option 3: Vinyl ester glass flake coating 750μm