How to determine if the corrosion level of scaffolding exceeds the standard?
To determine whether the corrosion level of the scaffold exceeds the standard, it is necessary to combine visual inspection, dimensional measurement, professional testing, and relevant standards and specifications. Specific measures can be taken from the following aspects:
1、 Appearance inspection: Preliminary assessment of corrosion status
Surface corrosion characteristics
Slight corrosion: A small amount of spot rust appears on the metal surface, without obvious rust layer accumulation. After wiping with a hard brush or cloth, there is no obvious damage to the base metal.
Moderate corrosion: A continuous rust layer forms on the surface, with localized flaking and rust areas exceeding 10% of the surface area of the component. After wiping, rough or small pits can be seen on the metal surface.
Severe corrosion: The rust layer is thick and extensively peeled off, and there are obvious pitting, pitting, or local perforation on the surface of the component. The corroded area exceeds 20% of the surface area of the component, or structural depressions appear.
Key inspection of critical parts
The welding nodes of upright and horizontal bars (such as the circular welding joints of buckle scaffolding): Corrosion may cause weld cracking or strength reduction.
Connecting components (such as pins, bolts, fasteners): Corrosion may cause jamming, deformation, and affect the reliability of the connection.
Weakly stressed areas (such as the bottom of the pole and the joint of the crossbar): Corrosion in these areas can easily cause overall structural instability.
2、 Dimensional measurement: Quantify the cross-sectional loss after corrosion
According to the "Unified Standard for Safety Technology of Construction Scaffolds" (GB 51210-2016) and other regulations, the following indicators are used to determine whether it exceeds the standard:
Thickness reduction of steel pipe wall
Measure the actual wall thickness of the corroded area with a caliper and compare it with the original wall thickness. When the reduction in wall thickness exceeds 10% of the original wall thickness, it is judged as exceeding the standard.
Example: For a steel pipe with an original wall thickness of 3.6mm, if the wall thickness is ≤ 3.24mm after corrosion, it exceeds the standard.
Local pit erosion depth
If local pitting occurs, measure the depth of the deepest pitting. When the depth of pit erosion exceeds 20% of the original wall thickness, or when the pit erosion causes a reduction of more than 10% in the effective area of the steel pipe section, it is judged as exceeding the standard.
Overall deformation and corrosion propagation
If corrosion is accompanied by steel pipe bending (exceeding the allowable deviation of the specification, such as vertical pole bending ≥ L/1000), component deformation (such as horizontal bar plug twisting), or corrosion has spread to the core area under stress (such as the welding point between the disc and the vertical pole of the buckle scaffold), even if the wall thickness does not exceed the standard, it should be judged as unqualified.
3、 Professional testing: assisting in determining hidden or severe corrosion
Magnetic thickness gauge detection
For components with a thick surface rust layer that has not peeled off, use a magnetic thickness gauge to measure the actual wall thickness under the rust layer to avoid masking the true degree of corrosion due to the surface rust layer.
Penetration testing (PT) or ultrasonic testing (UT)
For key parts such as welding nodes and bolt holes, determine whether cracks have occurred due to corrosion through penetration testing; Evaluate whether the internal structure has delamination or voids due to corrosion through ultrasonic testing.
Bearing capacity verification
For components with corrosion levels close to the critical value, the bearing capacity calculation should be carried out based on actual dimensions such as wall thickness and cross-sectional area. If the verification result shows that its bearing capacity is lower than 80% of the design value, it is judged as exceeding the standard.
