1.What are the corrosion characteristics of galvanized coatings in coastal areas?
Fast corrosion rate:
Coastal areas are highly corrosive environments (C5 grade, ISO 12944 standard). Chloride ions in salt spray will penetrate the passivation film (zinc oxide/zinc hydroxide) on the surface of the zinc coating, accelerating the electrochemical corrosion of zinc (the annual corrosion rate of zinc can reach 5-15μm, which is 3-10 times that of inland dry areas).
Special corrosion forms: In addition to uniform corrosion, local corrosion (such as crevice corrosion and pitting corrosion) is prone to occur, especially at the overlap of components, bolt connection parts, and surface scratches. The galvanized layer in these areas will be lost first and become the focus of maintenance.
2.What is the regular maintenance cycle for ordinary galvanized components?
After each maintenance, it is recommended to conduct a comprehensive inspection every 1-2 years and decide whether to perform maintenance again based on the degree of corrosion (e.g. local repainting can extend the life to 2 years, and overall heavy anti-corrosion can last 3-4 years).
3.How long is the maintenance period of thick zinc layer components?
The first maintenance period can be extended to 3-5 years (depending on the distance from the coast), but local weak areas (such as welding points and corners) need to be checked every 2 years.
Post-maintenance period: inspection every 1.5-2 years, and secondary maintenance every 3-4 years.
4.How long is the maintenance cycle for high-risk areas?
The zinc layer in these parts is prone to corrosion due to processing damage (such as high temperature welding destroying the zinc layer) or stress concentration, which requires a shorter maintenance cycle:
Inspect once every 6-12 months. If the area of local bottom exposure or white rust (zinc corrosion product) exceeds 5%, perform local repairs immediately (such as cold zinc spraying and zinc-rich paint repairs).
5.What are the key indicators for determining the maintenance cycle?
Remaining thickness of zinc layer: When the local thickness of the galvanized layer is less than 20μm, the base steel is easily exposed and begins to rust, and maintenance must be carried out immediately (can be detected by a coating thickness gauge).
Surface corrosion status: White rust (corrosion product of zinc, loose and weakly protective): When the area accounts for more than 10%, it needs to be cleaned and re-coated;
Red rust (rust on the base steel): Regardless of the size of the area, it is necessary to immediately remove the rust locally and re-apply zinc/anti-corrosion layer, otherwise the rust will spread rapidly.
Environmental mutation factors: If you encounter a typhoon or heavy rain (carrying a lot of sea salt), you need to conduct a comprehensive inspection within 1 month and deal with the washed or damaged galvanized layer in time.