1.What are the characteristics of a desert environment?
Low Humidity (Favorable Factor):
This is the most important favorable condition. An electrolyte (usually a water film) is essential for electrochemical corrosion. The extremely dry air and low average annual relative humidity in the desert make it difficult for a continuous and stable electrolyte film to form on the steel surface, significantly slowing the corrosion rate.
Large Diurnal Temperature Variation (Unfavorable Factor):
The desert experiences extreme heat during the day and cold at night. This temperature difference causes moisture in the air to condense on the metal surface at night. Despite the dry air, the daily condensation cycle provides the necessary moisture for corrosion. This is the main driving force behind desert corrosion.
High Ultraviolet Radiation (Unfavorable Factor):
Intense sunlight accelerates the oxidation of the zinc layer surface and may make the protective corrosion products (basic zinc carbonate) on the zinc layer surface less stable, exhibiting a certain aging effect.
2.What are the characteristics of the desert environment and its impact on corrosion?
High UV Radiation (Adverse Factor):
Strong sunlight accelerates the oxidation of the zinc coating surface and may destabilize the protective corrosion products (basic zinc carbonate) on the zinc coating surface, leading to aging.
Wind and Sand Abrasion (Adverse Factor):
Wind and sand contain a large number of hard sand particles, which can abrade and scratch the galvanized coating surface, physically damaging the integrity of the zinc coating, exposing the steel substrate, and creating a starting point for pitting corrosion.
Potential Saline-Alkali Soil (Adverse Factor):
The soil in some desert areas may be alkaline or contain salt. If the galvanized coil is used in structures close to the ground or in contact with sand, these soluble salts will dissolve in the condensation, forming a more conductive electrolyte that rapidly accelerates corrosion.
3.What are the protective mechanisms of galvanized coils?
Barrier protection: A complete zinc layer physically isolates the steel substrate from the environment.
Cathode protection: Even with minor scratches on the zinc layer, the exposed steel substrate acts as a cathode, receiving sacrificial protection from the zinc (anode).
4.What is the failure process of galvanized coil?
Due to the scarcity of moisture, the sacrificial anodic protection of zinc is intermittent (primarily during nighttime condensation).
The main protection comes from its barrier function.
Therefore, the thickness and integrity of the zinc layer are crucial in determining its lifespan.
5.What are some suggestions for using it in the desert?
Choose a sufficiently thick zinc coating:
When selecting galvanized coils, choose products with higher zinc coating designations (e.g., Z180, Z275 instead of Z60). A thicker zinc coating means longer wear time and better abrasion resistance. Hot-dip galvanized coils (such as SGCC) typically have a thicker zinc coating than electro-galvanized coils (such as SECC) and are therefore preferred.
Protect the surface during transportation and installation:
Avoid severely scratching the galvanized surface during hoisting, handling, and installation. Any scratches that penetrate to the substrate will become the starting point for future corrosion.
Post-treatment of cuts and severe scratches:
For severe damage caused by cut edges or installation, promptly apply zinc-rich paint for repair to restore the corrosion resistance of the area.