Material
Salt
Answer in brief
Salt is easy to convey and hard to keep: it cakes with humidity and corrodes most of what it touches.
Above roughly 75 percent relative humidity salt takes up water from the air, and when conditions swing back it recrystallises into a solid block.
- Control storage humidity rather than fighting the cake later.
- Choose stainless or non-metallic contact parts from the start.
- Expect abrasion from the crystal, which is harder than it looks.
Reviewed October 21, 2026 · Updated October 21, 2026
Handling challenges
Every salt handling problem traces back to water or to steel.
Caking and the critical humidity
Salt holds its condition below its critical relative humidity and takes up moisture above it.
The damage happens in the cycle: moisture dissolves crystal surfaces, drying recrystallises them, and the bridges that form between grains are solid.
- Dehumidified silo venting air rather than ambient breathing.
- Short storage times for fine grades, which cake fastest.
- Anti-caking agents where the product specification allows them.
Corrosion
Carbon steel in contact with damp salt corrodes quickly, and the rust is both a maintenance problem and a contamination source in food grades.
Stainless grades, polymer liners and non-metallic chutes are chosen for this reason, and fasteners and supports deserve the same attention as the contact surface.
Abrasion
Crystalline salt wears bends, screw flights and valve seats, particularly in dilute phase conveying at high velocity.
Lower velocity and protected impact zones extend life more than simply specifying a harder alloy.
Food and de-icing grades differ
Food-grade handling adds hygienic design, allergen-free cleaning and traceability, while de-icing salt is coarse, wet and handled outdoors with the corrosion problem multiplied.
What to establish before buying equipment
- Grade, particle size and anti-caking treatment.
- Humidity range inside the storage, not outside the building.
- Material of construction for every contact part including supports.
- Conveying velocity and the resulting wear expectation.
Material behavior
- Flowability
- Free flowing when dry
- Abrasiveness
- Moderate to high
- Cohesiveness
- Low when dry, severe caking after humidity cycling
- Moisture behavior
- Deliquescent above roughly 75 percent relative humidity
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