In the construction of water supply and drainage, fire-fighting pipelines, and steel structure supports, galvanized steel pipes are widely used. However, problems such as zinc peeling, flaking, exposure of the base metal, and local zinc layer shedding often occur. These issues not only affect the appearance but also accelerate the corrosion of the steel pipes and shorten their service life. So what are the main reasons for zinc peeling on galvanized steel pipes? How should it be handled on-site in an emergency? And how can it be prevented during regular construction?
First, briefly introduce two core situations:
Mild zinc loss: local peeling or small-area shedding, the zinc layer is only superficially detached, and the steel pipe substrate remains intact.
Severe zinc loss: large-area exposure of iron, zinc layer peeling off in whole pieces, accompanied by rust, and even pitting has appeared.
Then compare and analyze the two situations:
Slight zinc loss: This may be caused by transportation bumps, high-temperature welding, local friction, minor corrosion, and other reasons; it is relatively easy to handle and can be repaired directly on site; after repair, the original performance is basically restored.
Severe zinc loss: This may be caused by defects in the galvanizing process, strong acid or alkali corrosion, long-term humidity, or significant welding damage; it is more difficult to handle, requiring rust removal and zinc supplementation, and in severe cases, pipe replacement may be needed; after repair, the lifespan will be shortened and regular maintenance is required.
Finally, analyze according to the application scenarios:
Scenario 1: Temporary zinc peeling from small bumps on the construction site → Apply cold galvanizing paint in small areas, which is quick to construct, low in cost, and does not affect the schedule.
Scenario 2: Large-area zinc peeling at welding joints → Must first grind and remove rust, then apply zinc-rich paint overall, otherwise rust is very likely to form and leak from the welding seams.
Scenario 3: Zinc peeling in outdoor long-term humid environments → Prefer to use hot-dip galvanized pipes, and add a topcoat for protection after construction to reduce later maintenance costs.
In summary, the core principle for dealing with zinc loss in galvanized steel pipes is: for minor zinc loss, perform timely spot repairs; for severe zinc loss, completely remove rust and re-galvanize. To fundamentally prevent the problem, the key is to control three points: first, the quality of galvanization when purchasing the pipes; second, protection during transportation and installation; third, timely repairs after welding. Only by managing the entire process well can the service life of galvanized steel pipes be maximally extended.