26. What is the corrosion condition of zinc coating in oil field?

With the development of China's petroleum industry, the use of galvanized steel pipes for crude oil transportation in oil fields has become increasingly widespread. Consequently, the zinc coating is subjected to corrosion in hydrogen sulfide-containing crude oil and hydrogen sulfide-rich layered water. This results in limited corrosion resistance of galvanized steel pipes under oil extraction conditions. However, studies indicate that in groundwater containing 240-400 mg/L hydrogen sulfide near oil wells, galvanized steel pipes exhibit a lifespan 5-6 times longer than non-galvanized counterparts.
If the galvanized steel pipe is annealed at 500～550℃ for ten minutes, the pure zinc layer will be transformed into an iron-zinc alloy layer. The corrosion resistance of the alloyed galvanized steel pipe is greatly improved than that of the unalloyed one.