Rust Is a Schedule Slip: Protecting Mold Bases Between Shop and Press
Coatings: match the protection to the pause length
Short-term indoor storage needs only a light oil film; weeks to months call for a proper rust-preventive coating on machined surfaces; sea freight or long storage needs coating plus barrier packaging. The common failure is using indoor-grade oil on a part that then sits in a container for six weeks.
Coating discipline matters as much as the coating: every machined surface, including drilled water lines and threads, gets covered. A single uncooled water circuit is enough to start rust inside the plate where nobody can see it.
Barrier packaging and desiccants that actually work
VCI (vapour corrosion inhibitor) papers and films work well when the package is sealed and the VCI is close to the metal; they do nothing in a breathable crate. Desiccants reduce the humidity inside the wrap, and their quantity should follow the wrapped volume, not habit.
For sea freight: coated surfaces, VCI wrap, sealed barrier bag, desiccant, crated with plates supported flat. Molds with cooling circuits should have circuits drained and flushed, ports plugged.
Receiving inspection: check before the coating comes off
Inspect on arrival before removing coatings where possible: crate condition, wrap integrity, then a coating-on visual, then strip and re-check. Catching transit rust at the dock is a claim; catching it a month later is a repair.
In storage, rotate: re-inspect long-stored plates on a schedule and re-coat where the film has thinned. A plate that arrives perfect and rusts in your own rack is the most avoidable loss in the industry.
FAQ
Is VCI enough by itself for sea freight?
For clean, coated parts in a truly sealed package, VCI plus desiccant is usually adequate. Bare machined faces or a leaking wrap void the protection - coating and barrier come first.
How should water lines be protected in storage?
Drain, flush, dry where possible, and plug the ports. Lines that hold water are the classic hidden rust source inside an otherwise fine plate.
What should I do if a plate shows light rust on arrival?
Photograph it, note it on the delivery documents, and inform the supplier immediately - then assess depth. Light surface rust on a ground face removes easily; pitting that reaches the working surface is a different conversation.
All figures above refer to standard product data sheets; final confirmation is subject to written quotation.