Rust is a storage problem before it is a steel problem.
Where rust starts
Exposed machined surfaces rust first, especially in humid storage or after water-tightness testing without drying. Cooling channels corrode from inside, where nobody looks until flow drops or fouling appears.
Condensation during temperature swings — moving a cold mold into warm humid air — is a classic trigger.
Habits that prevent it
Apply protective coatings to machined surfaces before storage, dry and blow out cooling circuits after testing, and store molds in conditions that avoid condensation.
At startup after storage, inspect for rust and treat early marks before they pit surfaces.
FAQ
Do coated surfaces still rust?
They rust where coating is skipped or rubbed off — edges, handling marks and lifting surfaces need attention.
Can internal channel rust be fixed?
Light fouling can be chemically cleaned; advanced pitting may affect heat transfer and needs engineering assessment.
Is a climate-controlled store required?
Not necessarily, but stable, dry storage conditions dramatically reduce corrosion events.
All figures above refer to standard product data sheets; final confirmation is subject to written quotation.