Black steel seamless pipes are uncoated seamless pipes, the dark color comes from iron oxide formed on its surface during the manufacturing process. When a steel pipe is forged, a black scale forms on its surface, giving it the finish seen on this type of pipe.
The material used in the black steel seamless steel pipe has good corrosion resistance, but if the black steel seamless steel pipe is in a strong alkali or strong acid environment, corrosion will occur, and certain anti-corrosion measures need to be taken. After the anti-corrosion work is completed, some procedures are required to check whether the anti-corrosion work is qualified. The detection method is as follows
Coating Inspection and Acceptance
1. During and after surface coating construction, the coated workpiece should be protected to prevent flying dust and other debris.
2. The treatment and inspection after coating should be consistent with the coating color, bright and bright color, no wrinkled skin, blistering, sagging and missing coating and other obvious defects.
For the measurement of coating film thickness, use a touch-type paint film thickness gauge to measure the paint film thickness. The paint film thickness gauge generally measures the thickness of 3 points and takes the average value.
1. The quality inspection is carried out by sampling inspection according to the design regulations.
2. Visually inspect root by root. The surface of the covering layer should be uniform, flat, without bubbles, and there should be no covering layer defects such as wrinkles, bulges and uneven edge pressing.
3. The thickness of the paint film is measured with a magnetic thickness gauge. Measure a point every 1.5 meters on the circumference of the two ends and the middle of the single-section steel pipe. The thickness of the paint film should meet two 85%:That is, the thickness of 85% of the measuring points meets the design requirements, and the minimum value of the measuring points that do not meet the thickness should not be less than 85% of the design thickness;
4. Check pinholes with a pinhole inspector, if pinholes are found, use a sandpaper grinder to polish and repaint;
5. If the thickness of the paint film is insufficient or there are pinholes, it should be re-checked after repairing and curing. If it is not qualified, it should be repaired again until it is qualified;
6. For adhesion inspection, use a hard tool to draw an included angle of 60 incisions on the coating for random inspection.The coating should be penetrated directly to the substrate, and the scribed part should be pasted with tape. After tearing off the tape, carefully observe the scratches, and the coating should not peel off. There are also samples painted under the same conditions for inspection.