1.What is the core difference between galvanized pipes and iron pipes?
Anti-corrosion principle: The galvanized layer (zinc layer) on the surface of the galvanized pipe acts as a "sacrificial anode" and is corroded first to protect the internal steel; after oxidation, the zinc layer forms a dense zinc oxide film, which further blocks the corrosive medium.
Iron pipes (ungalvanized) have no anti-corrosion layer, and the steel is in direct contact with air, water, etc., which makes it prone to electrochemical corrosion (rust). The rust is loose and cannot prevent further corrosion inside.
Basic life range: Galvanized pipe in normal environment (such as dry indoor): 15-30 years; humid/outdoor environment: 10-20 years; buried underground or in contact with corrosive media: 5-15 years (depending on the thickness of the zinc layer).
Iron pipe (ungalvanized) in normal environment (dry indoor): 5-10 years; in humid/outdoor environment: 3-5 years; buried underground or in contact with water/soil: 1-3 years (prone to rapid rust and perforation).
2.What is the difference in lifespan in a dry indoor environment?
Galvanized pipe: The zinc layer is almost not corroded, and the service life can reach 20-30 years, or even longer (rust may only begin after the zinc layer is damaged by mechanical wear).
Iron pipe: Although it corrodes slowly, the surface will gradually rust. It may rust through or the structural strength may decrease within 10 years. It needs to be regularly derusted and painted for maintenance, otherwise the service life will be shorter.
3.What is the difference in wet/outdoor service life?
Galvanized pipe: The zinc layer will corrode slowly (corrosion rate is about 5-10 microns per year). If the zinc layer thickness meets the standard (such as hot-dip galvanized layer thickness ≥ 85 microns), it can be maintained for 10-20 years without perforation.
Iron pipe: If exposed to rain and fog, it will be severely corroded in 3-5 years, with large areas of rust pits, and even leaks and breaks. Frequent maintenance (painting every 1-2 years) is required to extend the life to 5-8 years.
4.What is the difference in lifespan between pipes buried underground or in contact with water/soil (such as underground water pipes and oil pipelines)?
Galvanized pipe: Moisture, salt, and microorganisms in the soil will accelerate the corrosion of the zinc layer. If the soil is less corrosive (such as sandy soil), the service life is about 5-10 years; if it is saline-alkali land or swamp, the service life may be shortened to 3-5 years (additional anti-corrosion coating or cathodic protection is required).
Iron pipe: After being buried in the ground, due to electrochemical corrosion of the soil, it may rust and perforate in 1-2 years. Even painting is difficult to prevent moisture penetration, and the actual service life rarely exceeds 3 years.
5.What are the other key factors that affect life expectancy?
Galvanizing process: Hot-dip galvanized pipes (thick zinc layer, strong adhesion) have a lifespan 30%-50% longer than electro-galvanized pipes (thin zinc layer).
Maintenance: If iron pipes are regularly derusted and painted with anti-rust paint, their lifespan can be extended to a level close to that of galvanized pipes (but the maintenance cost is high); if the zinc layer of galvanized pipes is mechanically damaged (such as scratches, collisions) and is not repaired in time, rust will spread from the damaged area, greatly shortening their lifespan.
Pipe diameter and wall thickness: Under the same material, pipes with thicker walls (such as DN100 and above) have a larger rust margin, and their lifespan is 5-10 years longer than thin-walled pipes.