How To Prevent Steel Bars From Rusting

Release time：

2026-08-19

The essence of the rusting of channel steel is that carbon steel undergoes electrochemical corrosion in a humid/oxidizing environment. Channel steel has grooves and many corners, making it more prone to water accumulation and dust accumulation, thus being more susceptible to rust compared to flat plates. Below are three layers of solutions for you to implement: process treatment → production process → storage preservation.

I. What can be done in the process (most effective, solving the problem at the source) ?

Process	Anti-rust capability	Applicable scenarios	Key points
Hot-dip galvanizing (HDG)	★★★★★	Outdoor, structural channel steel	Most commonly used, zinc layer acts as a sacrificial anode for protection, with a lifespan of up to 20 years; pay attention to thorough cooling after galvanizing to avoid white rust
Electro-galvanizing / Cold-galvanizing	★★★	Indoor, short-term turnover	Thin zinc layer, good appearance, but corrosion resistance is far inferior to hot galvanizing
Epoxy zinc-rich primer + topcoat	★★★★	Steel structure projects, heavy-duty anti-corrosion	First, sandblast for rust removal to Sa2.5 standard, the zinc content of the primer should be ≥ 70%, then mix epoxy iron oxide intermediate paint + polyurethane topcoat
Anti-rust oil / Passivation agent	★★	Export shipping, short-term inventory	Inter-process anti-rust, low cost, requires regular reapplication
Alloying treatment (such as weather-resistant steel)	★★★★	Outdoor exposed structures	Form a dense rust layer by adding Cu, Cr, Ni, but the cost is high; ordinary Q235/Q355 do not have it

II. What to pay attention to during the production process

Acid washing must be quickly dried. After acid washing to remove rust, the surface has extremely high activity. If there is residual moisture, it will rust again within a few hours. Acid washing → water washing → neutralization → hot air drying should be continuous, and do not stack outdoors waiting.
Control the residual heat from rolling/cold drawing. When the steel leaves the cold bed, if the temperature is higher than the environment, it will condense ( "sweating" ) when exposed to humid air. It should be stacked after completely cooling to room temperature or leave ventilation gaps when stacking.
Handling of cutting/drilling edges. Cutting surfaces and drill edges are weak points for anti-rust (the galvanized layer is damaged), it should be re-coated with zinc-rich primer or galvanized repair paint after processing, and should not be exposed.
Avoid cross-contamination. Cutting fluid, hand sweat, acid-base residues on the production line will accelerate rusting. Wear gloves during transportation, separate the finished product area from the acid washing area.
Prevention of "white rust" on galvanized parts. If the hot galvanizing is not fully dried before tightly packaging, white rust (basic carbonate zinc) will form in a humid and sealed environment. Requirements: fully passivate and dry after galvanizing, add desiccant when packaging, separate channel steel with wooden strips and leave gaps.

III. Storage (warehouse/shipment) precautions

Raise and keep away from the ground: Use wooden blocks or steel supports to raise the bottom of the channel steel ≥ 15cm to prevent direct contact with ground moisture. Do not stack directly on cement ground.
Ventilation and dryness: The relative humidity of the warehouse should be controlled below 60%. Close windows on rainy days, and ventilate on sunny days; stack the channel steel with grooves facing down or sideways to avoid water accumulation and dust.
Classification and isolation: Store galvanized parts and black materials separately to avoid damage to the zinc layer from hard objects; separate different batches and specifications to reduce handling.
Cover but not seal: When covering with waterproof fabric, leave ventilation openings. Complete sealing will cause condensation due to temperature difference; place desiccant in the shipping container (at least 4–6 pieces per 20-foot container).
First-in, first-out: The validity period of anti-rust oil/passivation film is usually 3–6 months. Recheck and reapply if the inventory exceeds the period.
Avoid corrosive environments: Stay away from chemical plants, coastal salt spray areas, coal yards; if unavoidable, upgrade to hot galvanizing or coating solutions.

In summary, rely on oil for short-term, galvanizing for medium-term, and paint for long-term

Using anti-rust oil for transition between processes, choose hot galvanizing for finished products, and use epoxy zinc-rich coating system for heavy-duty anti-corrosion in outdoor areas; in production, focus on "drying" and "re-coating of cutting edges", and in storage, focus on "raising, ventilation, and no water accumulation in grooves".

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