How to Store and Handle CRGO Laminations to Avoid Rust and Coating Damage

1. Start from the real failure modes

Skip the theory for a moment. In practice, CRGO-Laminierungen usually fail in just a few ways:

• Brown/red rust on faces or edges
• White rust / stain under or around coating damage
• Cracked or flaked coating at burrs, edges, and bend points
• Print-through and dents from straps, hard dunnage, or point loads
• Warped laminations from bad stacking or leaning storage

Once these appear, you get higher core loss, noise issues, and awkward discussions about credit notes and “acceptable” defects. And a lot of rework that nobody budgeted.

Most of these problems are created vor the laminations ever reach the stacking table. Storage and handling either keep the coating doing its job, or quietly undo it.

Steel mills and electrical steel catalogs repeatedly stress: keep grain-oriented steel dry, avoid long storage, protect the coating and cut edges, and control humidity.

So the practical question becomes: what does that look like in a real warehouse and shop?

2. Target storage conditions for CRGO lamination stacks

You don’t need a cleanroom, but you do need discipline. CRGO is not regular mild steel sheet; once the coating is compromised, corrosion accelerates, especially at cut edges and punched areas.

Here’s a simple spec you can use internally (or drop into a purchase spec / storage SOP).

Recommended storage envelope for CRGO laminations

This table is usually enough to push a basic discussion with your warehouse team or 3PL from “it’s just steel” to “this behaves more like a semi-finished precision part”.

3. When CRGO laminations arrive: what purchasing and QA should actually check

Most rust and coating issues originate within the first week after arrival. Or even in the container, if you’re unlucky.

A fast but strict intake routine helps:

3.1 Before breaking any straps

1. Inspect outer packing
   • Look for crushed corners, broken bands, wet cardboard, mold on wooden pallets, or salt stains on the wrapping (sea freight).
   • If you see signs of water ingress, stop. Log photos and quarantine.
2. Check humidity indicators / desiccant status (if used)
   • Many export packs now include humidity cards and desiccant bags; if cards show a high reading (e.g., >60% or “change color” area), mark the batch as higher risk for early use.
3. Mark storage priority
   • Use a simple “use first” tag for suspect or older pallets. Old CRGO stock with broken coatings rusts faster than fresh coils.

3.2 After opening: first exposed laminations

Once you cut the bands and lift the top cover:

• Siehe top 10–20 laminations on each stack:
  • Any brown or red marks near edges?
  • Coating blisters, flaking, or matte areas where it’s clearly gone?
• Wipe a small area with a clean, dry, lint-free cloth:
  • If you pick up oily residue with fine orange dust, corrosion has started.

If you find defects:

• Isolate that stack, note ID, take photos.
• Decide: early-use, rework, or reject (see section 7 below).

Purchasing needs this feedback loop; otherwise, you keep buying the same packing specification and getting the same damage.

4. Warehouse storage: simple rules that actually get followed

You can write a 20-page procedure. Or something the storekeeper remembers on a busy day.

Aim for a few rules like this:

4.1 Where to put CRGO lamination pallets

• Keep them away from loading doors where humid air, rain, and dust come in.
• No storage under leaking roofs, near wash areas, or near openings for cooling towers, etc.
• Don’t push pallets hard against cold exterior walls; leave a small air gap.

Most steel producers note that packing alone cannot compensate for poor warehouse climate or very long storage time.

4.2 How to stack pallets and containers

• Stack at most two lamination pallets high (three only if supplier certifies pallet strength and you have good racks).
• Verwenden Sie flat, level, strong dunnage between pallets; avoid narrow timber that creates line contact and indentation.
• Never store lamination stacks leaning against a wall. They bend slowly. Then they never sit flat in the core.

4.3 Protecting open stacks

Once a pallet is opened and not fully processed:

• Wrap the exposed stacks with VCI paper or film, not ordinary PE only.
• Add small desiccant bags inside the wrap if RH is often high.
• Label the stack with open date and responsible department.
• Rotate open stacks: oldest opened, processed first.

You’re not aiming for perfect conditions, just for the steel to spend as few days as possible in “exposed, humid, unprotected” mode.

5. Handling CRGO laminations on the shop floor

Most coating damage and micro-scratches come from handling, not storage.

Mill and processor guidance for grain-oriented steel repeatedly highlights: avoid impact, bending, surface scratches, and contamination by oils and moisture from hands.

5.1 People and tools

• Gloves, always
  • Light, clean work gloves. Avoid dirty cotton that carries abrasive dust.
  • Bare hands leave sweat and salts; they start micro-corrosion, especially during breaks or overnight.
• Lifting gear
  • Verwenden Sie wide textile slings or vacuum lifters for bundles where possible.
  • Avoid chains or steel cables directly on lamination edges. Use edge protectors if there is no choice.
• Work surfaces
  • Benches and stacking tables should be clean, smooth, non-abrasive.
  • No welding spatter, no burrs, no trapped metal chips.

5.2 Moving lamination stacks

Short version: no dragging.

• Don’t drag laminations over each other or across tables. That’s how you create long scratches that break the coating and introduce additional losses.
• Lift and place stacks, even for small adjustments. Use simple aids like Teflon or UHMWPE strips on tables to make repositioning easier with less force.
• When separating laminations, avoid bending at one corner; slide in a thin plastic or wooden wedge to start the separation.

5.3 Contamination control

Try to keep three things away from lamination surfaces:

1. Abrasive dust / scale
   • Regularly clean cutting machines and stacking areas.
   • Skip grinding or cutting operations in the same small area if you can.
2. Oil, paint, or sealant overspray
   • Mask laminations if painting nearby.
   • Avoid spraying rust converters or primers in the same zone.
3. Water and water-based cleaners
   • If you muss clean, use manufacturer-approved solvents and dry the surface fully.
   • Avoid any cleaner that leaves residue, especially alkaline.

6. Export, long-distance shipping, and long-term storage

If you ship lamination stacks or pre-assembled cores across climate zones, your risk increases quickly. The container becomes a small climate chamber: hot by day, cool at night, condensation everywhere.

Experienced exporters of transformer cores and CRGO slit coils typically add three extra layers: moisture-safe packing, sealing, and rust-inhibiting materials.

6.1 Packing structure that actually works

From inside to outside, a robust scheme looks like this:

1. Lamination stacks
   • Strapped with protected corners, faces covered with interleaving sheets.
2. VCI layer
   • Wrap stacks in VCI paper or film, sealed as tightly as practical.
3. Desiccant
   • Add calculated desiccant bags inside the wrapped volume. Place indicators where receivers can inspect them on opening.
4. Shrink or stretch wrap
   • Wrap pallet or crate to prevent free moisture and dust entry.
5. Crate / pallet design
   • Use closed wooden crates or robust pallets with top covers, especially for sea freight.
   • Provide tie-down points so lashing doesn’t cut into the steel.

6.2 Long-term storage (> 6–12 months)

If laminations must be stored for a year or more (strategic stock, slow projects):

• Keep them in original packing as long as possible, plus added VCI and desiccant if climate is tough.
• Avoid repeated moves; each handling step is a chance for damage.
• Plan regular visual checks (every few months): inspect a small area under the packing to confirm no condensation or rust starting.

If you know storage will be very long from the start, it might be cheaper to arrange smaller, more frequent deliveries of CRGO laminations than to treat a warehouse as a museum.

7. When you still see rust or coating damage

It will happen. The key is to distinguish “cosmetic, manageable” from “core performance at risk”.

7.1 Typical scenarios and responses

• Light surface discoloration, no pitting
  • Often acceptable after careful cleaning with a lint-free cloth or manufacturer-approved solvent.
  • Keep these laminations in non-critical positions where possible.
• Edge rust on cut faces, no flaking into the stack
  • If shallow, some users accept it on small distribution transformers; others don’t.
  • Once rust bridges laminations and creates conductive paths, losses rise and noise can worsen.
• Coating cracked or missing over large areas
  • Risk of inter-laminar shorts and higher losses.
  • For critical cores, re-lamination or replacement is usually safer.

Define an internal decision tree:

• What is your “no discussion” rejection level?
• What level triggers engineering review?
• When can you accept with concession and documentation?

Without this, every rusty lamination becomes a negotiation between QA, production, and purchasing.

8. Simple checklists for day-to-day use

You can adapt these into a one-page SOP on the shop wall.

8.1 For purchasing / incoming inspection

• [ ] Check pallets / crates for water damage or crushed areas
• [ ] Confirm humidity indicators and desiccant status where available
• [ ] Inspect top laminations for rust, stains, and coating defects
• [ ] Photograph any suspect areas and link to batch ID
• [ ] Mark pallets “use first” if packing looks compromised
• [ ] Log arrival date and planned latest use date

8.2 For warehouse and production

• [ ] Store CRGO lamination stacks indoors, off the floor, away from doors
• [ ] Keep RH around storage racks as low as feasible
• [ ] Limit pallet stacking height and use flat dunnage only
• [ ] Avoid leaning stacks; always store flat and supported
• [ ] Once opened, wrap stacks with VCI and label open date
• [ ] Use gloves when touching laminations; no dragging or sliding
• [ ] Keep cutting and stacking areas clean and dry

Not glamorous. But very effective.

9. FAQ: CRGO lamination storage and handling