When stored outdoors, carbon steel pipes (CS pipe) are highly susceptible to rust due to the combined effects of rain, moisture, condensation caused by diurnal temperature variations, and corrosive substances in the air. To prevent rust, several measures need to be taken to isolate the pipes from these corrosive factors.
1. Site Selection and Elevation
a. Site Selection: Place the carbon steel pipes in a dry location with good drainage, avoiding low-lying areas prone to water accumulation. The ground should be flat, firm, and preferably hardened (e.g., concrete).
b. Elevation and Isolation: Use wooden planks, cement blocks, steel frames, stone, or rubber mats to isolate the pipes from the ground. Elevate the pipe stacks at least 300 mm above the ground to ensure air circulation and rapid drying at the bottom, preventing groundwater seepage and rainwater accumulation.
2. Stacking Standards
To prevent steel pipes from collapsing during stacking: Care must be taken when stacking carbon steel pipes to prevent them from collapsing due to excessive weight or uneven ground, which could lead to property damage or personal injury. To avoid this, the following measures should be taken:
a. Stabilize the stack shape
Use a crisscross or quincunx stacking pattern, separating layers with wooden blocks and aligning them vertically. This ensures the stability of the stack, prevents rolling and collapse, and also facilitates internal ventilation.
Fix wooden boards or rubber pads at the top of the steel pipes, and install supports or large bolts at the middle and ends of the pipes. This increases the stability and resistance to collapse during stacking.
b. Control the height: The stacking height should not be too high to avoid excessive pressure on the bottom pipes, which could lead to permanent bending and deformation.
c. Ensure consistent orientation: The pipe ends should ideally face the same direction for a neat and aesthetically pleasing appearance, as well as ease of inspection and rainwater drainage.
3. Proper Use of Supports
When stacking steel pipes, proper use of supports is crucial for ensuring the safety and stability of the pipes. The following are points to note when using supports:
a. Supports must be placed on a firm, level surface to effectively bear the weight.
b. The number and spacing of supports need to be considered comprehensively based on factors such as the length, weight, and material of the steel pipes to ensure that the supports can effectively support the weight of the steel pipes and maintain balance.
c. When using supports, adjustments and shims are necessary as needed to ensure balance between the supports and the steel pipes.
4. Rain Protection
Tight Covering: The pipe stacks must be tightly covered with waterproof, durable tarpaulins (such as PE/PVC coated fabric).
Covering Techniques: The tarpaulin should completely cover the pipe stack, with a slight angle to ensure rainwater can drain away smoothly and prevent water accumulation at the top or middle.
The edges of the tarpaulin should be firmly pressed down to prevent it from being blown open by the wind.
5. Other Auxiliary Measures – For Long-Term Storage
If the expected storage time is long (more than 3 months), consider the following enhanced protection:
Apply Rust-Inhibiting Oil/Agent: Apply a thin layer of specialized rust-inhibiting oil or agent to the surface of the steel pipe. This isolates it from external air, water, and impurities, thus preventing rust. This is a very effective short- to medium-term protection method.
Pipe End Sealing: For threaded or
precision tubes, use plastic or metal caps to seal the pipe ends to prevent moisture and foreign objects from entering the pipe.
6. Categorized Management and Maintenance
Categorized Storage: Steel pipes of different materials, specifications, and batch numbers should be stacked separately with clear labels for easy management and adherence to the "first-in, first-out" (FIFO) principle.
Regular Inspection: A comprehensive inspection is recommended monthly, with increased frequency during the rainy season.
"First-in, First-out" Principle: Ensure that steel pipes that enter the warehouse first are issued first to prevent some pipes from rusting more rapidly due to prolonged storage.
Following the 6 points above, while it cannot completely eliminate the natural corrosion of carbon steel pipes, it can significantly slow down the corrosion process, effectively reducing inventory losses and economic damage, making it a crucial aspect of warehouse management.
What to do if steel pipes stored outdoors rust?
When steel pipes are stored outdoors, they are prone to rusting due to factors such as oxygen, moisture, and impurities in the air. The most common type is surface rust.
Surface rust typically refers to a thin, uniform layer of iron oxide (rust) that naturally forms on the surface of the steel after contact with air and moisture. It has not yet caused severe pitting or deep corrosion to the base material of the steel pipe, so its treatment is relatively simple and not a major concern.
Rust Removal Methods:
For large-diameter steel pipes, the most common rust removal method in factories is mechanical rust removal using specialized equipment (such as sandblasting and shot blasting). The advantage is its extremely high efficiency, making it suitable for large-scale processing.
a. Sandblasting: Sandblasting removes rust, old paint, and other contaminants from steel pipes, creating a uniform, pitted surface. This increases adhesion between the coating and metal in subsequent
anti-corrosion processes, improving the coating's effectiveness and lifespan. Sandblasting is suitable for both pipes and plates, and is ideal for large-scale, concentrated rust removal. However, it generates significant dust, so workers should wear goggles, helmets, and masks.
b. Shot blasting: The steel pipe rotates and advances within the cleaning chamber, impacting the surface with high-speed projectiles (steel shot) to thoroughly remove rust and scale. This method offers the best rust removal quality, achieving Sa2.5 or higher, and creates surface roughness, significantly improving coating adhesion.
Applicable scenarios: Large steel pipe plants, anti-corrosion plants, or projects with extremely high coating requirements (such as subsea pipelines and critical structural pipes).
Other rust removal methods:
Acid pickling: This method uses an acidic solution (usually hydrochloric acid or sulfuric acid) to react chemically with the rust, dissolving it. Before acid pickling, the grease on the pipe wall should be removed, as grease can prevent the pickling solution from reaching the pipe wall, affecting the rust removal effect. After rust removal, before painting, wipe the surface of the pipe clean with cotton yarn or a rag to remove any dust. The advantage is that it can completely remove rust, including rust in crevices, leaving the surface very clean.
Applicable scenarios: Used before steel pipes leave the factory or before special anti-corrosion treatments such as
hot-dip galvanizing. It is generally not recommended for steel pipes already stored outdoors, as on-site implementation is difficult.
Rust treatment principles:
1. Assess the intended use: The final use of the steel pipe must be clearly defined before treatment. Is it for load-bearing structures, water supply, gas supply, or pile pipes? Different uses require different surface treatment levels.
2. Avoid damaging the base material: All treatment methods should be based on the premise of not damaging the steel pipe substrate.
3. Timely Treatment: If surface rust is left untreated, it will continue to develop, absorbing more moisture and eventually turning into thicker rust or pitting that is more difficult to treat.
Note: After rust removal from carbon steel pipes, the metal substrate is completely exposed and will rust again at a faster rate when exposed to air. Therefore, immediate anti-corrosion treatment is essential, along with improved storage conditions.
Read more: Black Steel Pipe vs. Galvanized Steel Pipe or Steel Pipe Dimensions & Sizes Chart
sales@hu-steel.com
English
Español
