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Regulations for the thickness of anticorrosive coatings on steel structures and introduction of measuring instruments

Regulations for the thickness of anticorrosive coatings on steel structures and introduction of measuring instruments


Steel structure anticorrosive paint spray coating is an oily or non-oily colloidal solution, which can be coated on the surface of steel structure components to form a coating film to prevent steel structure components from being corroded.

Steel structure bridges at home and abroad usually adopt the anti-corrosion system of "base coating + intermediate coating + top coating". The base coating materials are divided into metal spraying and heavy coating anti-corrosion. The metal spraying materials are divided into zinc, aluminum, zinc aluminum alloy and so on. Heavy-duty anti-corrosion primer materials are also divided into inorganic zinc-rich coatings and epoxy zinc-rich coatings. The middle coating mostly uses epoxy mica coating, and the top coating materials are divided into phenylene acid polyurethane coatings, siloxane coatings and fluorocarbon coatings.

According to Article 5.2.3 of GB/T50046-2018, the surface protection of steel structure should meet the requirements of the following table.

Minimum spray thickness requirement of anti-corrosion coating (unit: μm)Requirement for the service life of the protective layer
Strong corrosive environmentModerately corrosive environmentWeakly corrosive environment
320μm280240Above 15 years
28024020011~15 years 
2402001606~10 years
2001601202~5 years

The thickness of the coating film and the measuring method

A. If the number of coating passes and coating thickness are not required by the design, the total dry film thickness of the steel structure coating should be in accordance with the "Code for Acceptance of Construction Quality of Steel Structure Engineering" (GB50205-2001). Outdoor is 150μm, and the allowable deviation is -25μm. Generally, it should be painted 4-5 times, and the allowable deviation of the dry film thickness of the Xu layer per pass is 5μm

B. Measuring method of coating film thickness.

1. Prepare measuring instruments and coating thickness gauges, and know the requirements of the construction process.

2. Observation and inspection: uniform application, complete coating film, and good adhesion.

3. Instrument measurement: When inspecting with a dry coating film measuring instrument, it is required to select three measuring points with a distance of 50mm in the measured area to determine the dry coating film thickness, and then take the weighted average of the coating film thickness (error -25μm) ) As the thickness of the place.

Introduction to the instrument for measuring the anticorrosive coating of steel structures:

If you use Guoou GTS8202 iron-aluminum dual-purpose split coating thickness gauge,

Using magnetic and eddy current effects, two coating thickness measurement methods can measure the thickness of the non-magnetic coating on the magnetic metal substrate and the thickness of the non-conductive coating on the non-magnetic metal substrate; this coating thickness measurement The instrument can quickly and automatically identify ferrous substrates and non-ferrous substrates; the accuracy reaches 1±2.5%H, where H represents the actual thickness of the coating currently measured, and the built-in Bluetooth function makes it easy to manage data and share statistics with mobile phones.