1.What is the rate of zinc loss in rural environments?
Environmental characteristics: clean air, low humidity, almost no industrial pollutants and salt, the main corrosion factors are moisture in the atmosphere and a small amount of carbon dioxide (forming weak carbonic acid).
Loss rate: usually 0.5-2 μm / year.
2.What is the rate of zinc loss in an urban environment?
Environmental characteristics: There is a certain amount of automobile exhaust (including sulfur dioxide and nitrogen oxides), dust, moderate humidity, and possible mild industrial pollution.
Loss rate: Generally 2-8 μm/year.
If the zinc layer thickness is 85 μm, the theoretical life span is about 10-40 years, depending on the industrial density of the city.
3.What are the characteristics of a marine/coastal environment? What is the corrosion rate of the zinc layer?
Environmental characteristics: high humidity (often over 80%), large amounts of chloride ions (salt spray) in the air. Chloride ions have strong penetrating power and will destroy the passivation film of the zinc layer, accelerating electrochemical corrosion.
Loss rate:
Within 1 km from the coastline (high salt fog area): 10-30 μm/year;
1-5 km from the coastline (medium salt fog area): 5-15 μm/year;
More than 5 km from the coastline (low salt fog area): 3-8 μm/year.
4.What is the rate of zinc loss in an industrial environment?
Light industrial area (medium to high corrosion)
Environmental characteristics: There is a small amount of industrial waste gas (such as a small amount of sulfur dioxide and dust), such as around food processing and textile industries.
Loss rate: 5-15 μm/year, close to the level of urban industrial areas.
Heavy industrial area (extremely high corrosion)
Environmental characteristics: a large amount of industrial pollutants, such as sulfur dioxide (coal burning, chemical industry), hydrogen sulfide (wastewater treatment, metallurgy), dust (steel, cement), forming an acidic or alkaline corrosive environment.
Loss rate: 15-50 μm / year, or even higher.
5.What is the zinc layer loss rate in special environments?
High temperature and high humidity environment (such as tropical rainy season, greenhouse)
Environmental characteristics: temperature>30℃, humidity>90%, accelerating the electrochemical corrosion reaction of zinc.
Depletion rate: 5-20 μm/year, if accompanied by high humidity + pollutants (such as fertilizer vapor in agricultural greenhouses), the rate can reach 20-30 μm/year.
Soil environment (such as buried galvanized steel pipes)
Environmental characteristics: depends on soil pH, moisture content, resistivity (clay> sand), microorganisms (such as sulfate-reducing bacteria).
Neutral soil (pH 6-8): 2-5 μm/year; ◦ Acidic soil (pH <5) or saline-alkali land (pH >9): 10-30 μm/year;
Clay with high organic matter/poor air permeability: due to lack of oxygen and microbial action, local corrosion may occur, and the loss rate fluctuates greatly (5-50 μm/year).