Construction Technology of Corrosion-Resistant Alloy Protective Layer for Inner Wall of Sulfur-Containing Crude Oil Storage Tanks

Corrosion of the inner wall of sulfur-containing crude oil storage tanks is mainly caused by hydrogen sulfide (H₂S) and sulfides. Corrosion-resistant alloy protective layers (such as 2205 duplex stainless steel or Inconel 625) are required to resist pitting corrosion and stress corrosion cracking. Before construction, sandblasting treatment is required (Sa2.5 grade, roughness 40~75μm), and epoxy conductive primer is applied (thickness ≥80μm) to ensure the bonding strength between the substrate and the alloy layer.

The construction process is divided into three steps: 1) Alloy layer surfacing welding adopts TIG welding, and the interpass temperature is controlled below 150℃ to avoid intergranular corrosion; 2) Spraying nickel-based alloy (such as NiCr-Cr3C2), bonding strength ≥35MPa; 3) Sealing treatment uses fluorocarbon topcoat (acid and alkali resistance ≥1000h), overall thickness ≥300μm. Key nodes need to be subjected to X-ray flaw detection (pass rate ≥98%) and electrochemical impedance testing (corrosion rate ≤0.1mm/a).

After a coastal refinery adopted this process, the corrosion rate of the inner wall of the storage tank decreased from 0.8mm/a to 0.05mm/a, and the service life was extended to more than 15 years. The maintenance cost is reduced by 40% compared with the traditional carbon steel + coating scheme, which meets the Sinopec anti-corrosion standards for high-sulfur crude oil storage tanks.