Research and Application of Waterborne Epoxy Coatings for Inner Walls of Storage Tanks and Floating Ships

introduction

The corrosion form of petroleum storage tanks does not exist alone, but is caused by one or both of electrochemical corrosion and chemical corrosion

Anti-corrosion coating for inner surface of floating vessel

According to data research, it can be found that there are the following types of anti-corrosion coatings commonly used in the market:

(1) Epoxy coal tar pitch anticorrosive paint

(2) Epoxy primer + epoxy topcoat

(3) Water-based inorganic zinc-rich primer + water-based epoxy anticorrosive topcoat

Construction technology of water-based paint on the inner surface of floating vessel

The interior of the pontoon is a confined space with a closed and complex structure.

(1) Surface pretreatment

The surface treatment of the substrate has a great influence on the anti-corrosion effect and life of the coating.

(2) Construction of water-based inorganic zinc-rich primer

The base material of the pontoon needs to be prefabricated and sprayed in the workshop, and the dry film thickness should not be too thick, otherwise the coating will crack and lose its anti-corrosion effect.

The construction method of the water-based inorganic zinc-rich coating can be brushed, rolled or sprayed
.
Before large-area construction, some special parts, such as special-shaped structures, weld edges, etc.
, need to be pre-coated to ensure that each part is covered by the coating
.

The curing of water-based inorganic zinc-rich coatings requires the participation of water, but excessive air humidity will affect the volatilization of moisture in the coating.
The recommended environmental humidity for construction and maintenance is 60% to 80%
.
The performance is shown in Table 1
.

Table 1 Performance of water-based inorganic zinc-rich coatings

(3) Hoisting and water testing

Hoist the floating vessel and conduct a water pressure test.
After passing the test, perform surface treatment on the inner wall and repair the damaged parts
.

(4) Construction of water-based epoxy topcoat

The interior of the pontoon is a relatively small and poorly ventilated environment.
Therefore, when the water-based paint is constructed in the pontoon, the volatilization of the water in the paint can easily cause the increase of the air humidity in the cabin
.
When the air humidity is too high, the moisture in the coating cannot be volatilized, which will affect the normal curing of the coating, causing problems such as pinholes, softness, and sagging
.
Common methods for controlling humidity include: (1) The exhaust fan blows air at the entrance.
The disadvantage of this method is that each cabin has only one small hole for people to enter and exit, and the air exchange is not ideal; (2) compressed air ventilation; (3) Heating and dehumidifying equipment
.

Waterborne epoxy coatings have good application adaptability.
You can choose a variety of construction methods for construction.
Before large-scale construction, some special parts, such as special-shaped structures, weld edges, etc.
, need to be pre-coated to ensure that each part is covered.
Covered by coating
.
The performance is shown in Table 2
.

Table 2 Performance of Waterborne Epoxy Coatings

(5) Inspection and acceptance

After the coating is cured, the anti-corrosion coating shall be inspected and accepted in accordance with the technical indicators and standards specified in the technical specifications
.

Concluding remarks

For anti-corrosion construction in small and confined spaces such as floating ships, paint selection should first consider the feasibility and safety of construction
.
Water-based paint is easy to apply, has excellent anti-corrosion performance, low VOC content, and the solvent is mainly water.
When constructing in a confined space such as a floating boat, water volatilizes into the air and will not pollute the environment, and there will be no potential safety hazards such as explosion, which is very ideal.
Anti-corrosion material inside the pontoon
.
In the future, the application of water-based coatings in the anti-corrosion of petroleum storage tanks will become more and more extensive
.

Author | Chen Jun (CNOOC (China) Co.
, Ltd.
Tianjin Branch)

Source: "Coating and Protection" magazine