- First: Determine the anti-corrosion construction process
1. Exterior wall construction process: pipe rust removal - primer application - first coat of topcoat - second coat of topcoat - wrapping glass silk cloth - topcoat - topcoat.
2. Inner wall construction process: pipeline rust removal - primer application - first coat of topcoat - second coat of topcoat - third coat of topcoat.
- Second: Carry out rust removal
Before applying primer, the surface of the pipe should be cleaned of grease, ash, rust, and oxide scale. The quality standard of sandblasting rust removal reaches Sa2.5 level.
Apply primer after removing rust from the pipe surface. The time interval should not exceed 8 hours. When applying primer, the base surface should be dry. The primer should be applied evenly and fully without any clumping or bubbling. The primer should not be applied within the range of 150 to 250mm at both ends of the pipe.
The epoxy coal pitch anti-corrosion steel pipe coating is a two-component, room temperature curing coating; the glass fiber cloth is dry, dewaxed, untwisted, edge-sealed, medium alkali, with a warp and weft density of 10+12 threads/cm~12+12 threads/ cm glass fiber cloth. Immediately after the topcoat is applied, wrap the glass silk cloth. The width of the edge of the glass cloth is 30 to 40 mm. The overlap length of the joints is not less than 100 mm. The overlap joints of each layer are staggered. The oil penetration rate of glass fiber cloth is more than 95%. There should be no gap larger than 50mm+50mm. Leave a 150~250mm stepped gap at the end of the pipe.
The construction of pipeline interfaces should be carried out after passing the welding pressure test. The old and new anti-corrosion edges should not be less than 50mm, the overlap length of the joints should not be less than 100mm, and the joints should be firmly and tightly bonded.
- Third: Anti-corrosion testing
1. Quality inspection shall be carried out by sampling inspection according to the design regulations.
2. Visually inspect each root. The surface of the covering layer should be uniform, smooth, and free of covering layer defects such as bubbles, wrinkles, bulges, and uneven edge pressure.
3. The paint film thickness is measured with a magnetic thickness gauge. Measure a point every 1.5 meters on both ends and the middle circumference of the single-section steel pipe. The paint film thickness should meet two 85%: that is, 85% of the measuring point thickness reaches the design According to the requirements, the minimum value of measuring points that cannot reach the thickness should not be less than 85% of the design thickness.
4. Use a pinhole detector to check for pinholes. If pinholes are found, use a sandpaper grinder to grind and recoat.
5. If the paint film thickness is insufficient or there are pinholes, it should be re-examined after repair and solidification. If it is unqualified, it should be repaired again until it is qualified.
6. To check the adhesion, use a hard tool to make a cut with an angle of 60° on the coating for spot inspection. The cut should be made through the coating directly to the base material, and the cut part should be pasted with tape. After tearing off the tape, observe the scratch. The coating should be free of peeling. A sample painted under the same conditions can also be inspected.
- Fourth: Anti-corrosion acceptance
1. During and after surface coating construction, the painted workpieces should be protected from flying dust and other debris.
2. During post-painting inspection, the coating should be consistent in color, bright and bright, and free of defects such as wrinkles, blistering, sagging, and missing paint.
3. To measure the thickness of the coating film, use a contact-type paint film thickness gauge to measure the thickness of the paint film. The paint film thickness gauge generally measures the thickness at 3 points and takes the average value.
