Commonly used steel structure anti-corrosion coating matching practices!

Common method of anti-corrosion of steel structure

Weathering steel corrosion resistance is better than the general structural steel steel steel is called weathering steel, generally contains phosphorus, copper, nickel, chromium, titanium and other metals, so that the metal surface to form a protective layer to improve corrosion resistance

1 Introduction

The anti-corrosion method of steel structure has anti-corrosion coating; Zinc, aluminum and other metal protective layers formed by various processes; cathodic protection measures; Weathering steel; A combination of the above anti-corrosion schemes

According to article 3.

4.

In terms of design, the following ways should be taken to control the corrosion of steel structures: 1.

On the basis of the above design measures, the use of anti-corrosion coatings can achieve a relatively ideal anti-corrosion effect

2 Anti-corrosion coatings

Anti-corrosion coatings (paints) are the most common anti-corrosion method of steel structures

According to Article 5.

Steel structure bridges at home and abroad usually adopt the anti-corrosion system of "primer + medium coating + topcoating", and the primer materials are divided into metal spraying and coating heavy anti-corrosion

3, all kinds of paint doorway

Common primers for steel structures are alkyd anti-rust paint (ordinary anti-rust paint), inorganic zinc-rich primer, epoxy zinc-rich primer, high chlorinated polyethylene primer (used for acid-alkali-resistant chemical industry steel structure), epoxy coal asphalt primer (used for underground steel structure).

Common intermediate paints in steel structures include epoxy cloud iron intermediate paint, high chlorinated polyethylene intermediate paint, epoxy coal asphalt intermediate paint and so on
.
Common topcoats for steel structures are acrylic paint and fluorocarbon paint
.
Alkyd anti-rust paint (ordinary anti-rust paint) is our common redtong kind of paint, can only be matched with alkyd magnetic paint, blend paint and other ordinary paint, for the corrosion is not serious, the appearance and anti-corrosion requirements are not high in the coating field, only in the ordinary atmospheric environment has a good anti-rust effect, not suitable for chemical, seaside, high weather resistance requirements of the coating field
.
It has low requirements for the surface treatment of the steel structure before painting, and the surface of the steel structure can be dynamically descaled and manually polished to the St2 level to be normally coated
.
Inorganic oxygen-enriched primer (generally supporting epoxy cloud iron intermediate paint and a variety of high-performance two-component topcoats), with electrochemical anti-rust and corrosion, corrosion inhibition and other multiple anti-rust effects, salt spray resistance, solvent resistance, alkali resistance, oil
resistance.
The paint is resistant to high temperatures and can be used as an anti-rust primer for high temperature pipes
.
Epoxy zinc-rich primer, a supporting primer for heavy anti-corrosion coatings, has cathodic protection effect, suitable for storage tanks, containers, steel structures, steel pipes, marine platforms, ships, seaport facilities and harsh anti-corrosion environments
of the bottom coating.

In steel structures, bridge heavy corrosion protection systems, the intermediate paint is usually used epoxy cloud iron intermediate paint, although it can also be used
as an anti-rust primer.
Epoxy cloud iron intermediate paint (primer) is a two-can cold-curing epoxy paint
composed of gray mica iron oxide as a pigment, epoxy resin as the base material, polyamide resin as a curing agent, etc.
Due to the superior properties of mica iron oxide and epoxy resin, the paint film is tough and has good adhesion, flexibility, wear resistance and sealing properties
.
Epoxy cloud iron paint is generally used as a mid-layer paint, and is used in conjunction with epoxy zinc-enriched primers to enhance the sealing and anti-corrosion properties between coatings
.
In many large-scale steel anti-rust and anti-corrosion projects, the figure of epoxy cloud iron intermediate paint will be seen
.
It can not only improve the anti-rust effect, but also save costs
.
Epoxy cloud iron intermediate paint is a very cost-effective paint
.

4.
About the strong strip of painting

According to the "Steel Structure Engineering Construction Quality Acceptance Standards" GB50205-2020, Article 13.
2.
3 anti-corrosion coatings, coating times, coating intervals, coating thickness should meet the requirements of
design documents and coating product standards.
When the design has no requirements for coating thickness, the total thickness of the coating dry paint film: outdoor should not be less than 150μm, indoor should not be less than 125μm
.

Inspection quantity: 10% of the components should be spot checked according to the number of components, and the same type of components should not be less than 3 pieces
.

Inspection method: check
with dry paint film thickness gauge.
Each component is tested at 5 locations, and the value at each place is the average of the dry paint film thickness of the coating at 3 50mm measurement points
.
The permissible deviation of the paint film thickness should be -25 μm
.

5.
Testing of coating (according to the specification "Technical Standard for On-site Testing of Steel Structures") (GB/T 50621-2010)

5.
1 Detection of the thickness of the anti-corrosion coating:

The maximum range should not be less than 1200 μm, the minimum resolution should not be greater than 2 μm, and the relative error of the indication value should not be greater than 3%.

The same component should be tested in 5 places, each of which is the average
of the coating thickness of 3 measurement points 50 mm apart.

5.
2 Thickness of anti-corrosion coating:

2) When the design has no requirements for the thickness of the coating, the total thickness of the coating dry paint film should be 150μm outdoors, 125μm indoors, and its allowable deviation should be -25μm
.

6.
Did you know? Some data on corrosion and corrosion protection

According to the corrosion of the steel pile tested by scholars on the Kiel Waterfront in the United States after 5 years, the corrosion rate of uncoated steel calculated is shown in the following table
.

The following technical parameters are excerpted from the "Anti-corrosion Design Standard for Industrial Buildings" GB/T50046-2018