How to determine if an F-Style can is corroded?
Nov 07, 2025
I. F-Style Can Corrosion Inspection Methods
1. Visual Inspection
Use a strong flashlight and a magnifying glass to inspect the interior and exterior walls of the can, focusing on welds, pipe connections, and areas of water accumulation at the bottom. Be cautious if uniform corrosion results in a wall thickness reduction exceeding 10% of the original thickness.
On the exterior wall, inspect areas prone to localized corrosion, such as where water enters the insulation layer and where windbreaks are connected.
Thickness Measurement
Use an ultrasonic thickness gauge to measure the corroded area in a grid pattern (distance between adjacent measurement points ≤ 50cm). If the localized thinning exceeds 20% of the standard wall thickness or the remaining thickness is below the design minimum allowable value, the can must be immediately decommissioned.
High-temperature cans can be measured using electromagnetic ultrasonic thickness measurement, while insulated cans can be measured using pulsed eddy current technology.
Corrosion Product Analysis
Collect corrosion products and test for components such as chloride ions and sulfides. Coastal areas require special attention to salt spray corrosion (rates can reach 0.5mm/year). II. Key Corrosion Areas
1. Inner Wall
The area 0-300mm above the bottom weld and at the level fluctuation point (oil-gas interface) is susceptible to electrochemical corrosion due to chlorides, sulfides, and other substances in the sedimentary water.
2. Tank Bottom
The medium side is susceptible to perforation due to erosion and friction with columns. The soil side is susceptible to oxygen concentration cell corrosion due to water seepage or uneven aeration in the foundation.
III. Auxiliary Detection Techniques
1. Acoustic Emission Testing: Online monitoring of bottom plate corrosion, supplemented by high-frequency guided wave technology.
2. Eddy Current Testing: Suitable for detecting surface and near-surface defects in conductive materials, but is limited by the skin effect.
IV. Corrosion Protection Standards
The inner wall coating thickness must be ≥200μm (standard grade) to ≥400μm (deposited water area in crude oil tanks). The outer wall anti-corrosion material should be selected based on atmospheric corrosion resistance.
