Protecting Inverters from Salt Air and Container Condensation
Inverters are usually ruined by moisture and salt long before they fail in service, and the protection has to be specified at the packing bench.
Representative scenario, not a specific client engagement. This page describes how a shipment of this kind is genuinely handled — the constraints, the approach, and where it commonly goes wrong. It does not name or describe a real Transeasy customer. Our two documented project moves are the Mexico container move and the India overweight cargo delivery.
The situation
Electrical inverters moving from South China to the Gulf or South Asia meet two distinct moisture problems that are often treated as one. The first is condensation inside the container: cargo stuffed on a humid Shenzhen morning seals in air with a high dew point, and when the steel shell cools overnight or on a cooler leg of the voyage, water forms on the roof and walls and falls back onto the cargo. Packaging timber releases its own moisture into the same air.
The second is salt. Aerosol reaches deck-stowed containers through vents and door seals, and chloride on a circuit board, a terminal block or a connector pin begins corroding long before the unit is energised. An enclosure rating describes an installed product in service, not a sealed carton crossing the Indian Ocean, so an IP-rated cabinet protects nothing during transit. Damage is typically discovered at commissioning, months after the packing decision that caused it.
What made it difficult
- Condensation is created by the air and materials sealed into the container at origin, so nothing done at destination can prevent it.
- Cargo policies exclude insufficiency of packing, and insurers routinely treat damp damage as a packing question rather than a transit peril.
- Quayside and warehouse dwell in Gulf and South Asian summer heat intensifies whatever moisture is already inside the packaging.
- Corrosion surfaces at commissioning rather than at delivery, by which time the discharge survey window has usually closed.
How it is approached
Protection is specified rather than improvised. The moisture load is calculated from cargo volume, packaging timber and the expected voyage, and desiccant quantity follows from that calculation instead of from habit, because a handful of sachets in a forty-foot container is decoration. Timber is kiln-dried and checked for moisture content before use, and the container itself is inspected for a wet floor, daylight at the seams and a failed door gasket before anything is loaded.
Sensitive assemblies travel inside a sealed barrier rather than a carton. An aluminium-laminate barrier bag with desiccant inside holds a dry micro-environment independent of the container, vapour corrosion inhibitor film protects exposed metalwork where a full barrier is impractical, and a humidity indicator card inside each bag makes the condition visible at opening. Container liners and dunnage keep cargo clear of the walls and roof, where dripping water lands first.
Routing carries real weight here. Under-deck stowage reduces salt exposure and temperature swing, a direct service shortens the exposure window compared with a transhipment routing that adds days in a hot port, and where a unit is genuinely too sensitive the air option is compared on total cost including the value of a commissioning delay. Booking is planned around the site's ability to take delivery rather than leaving units standing on a quay.
Evidence is built into the pack so a problem can be attributed rather than argued. Photographs of the loaded container, a record of the barrier and desiccant specification used, indicator cards read at opening, and a joint survey before units go into storage together establish whether moisture entered at origin, in transit or on site. That record is also what allows a repeat consignment to be corrected at the right point instead of over-packed everywhere.
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Takeaways
- Condensation is designed into a shipment at the packing bench and cannot be reversed anywhere downstream.
- Desiccant quantity is a calculation from cargo volume and packaging moisture, not a fixed number of sachets per container.
- An enclosure rating protects an installed inverter, not a packed one, so transit protection is specified separately.
- Humidity indicator cards and loading photographs turn a disputed corrosion claim into an evidenced one.
Frequently asked
Because the water comes from inside. Warm, humid air sealed in at origin holds moisture that condenses on the steel roof and walls whenever they cool below the dew point, then drips back onto the cargo, an effect commonly called container rain. Packaging timber and the goods themselves add to that moisture load, so a sound, watertight container can still deliver wet cargo.
It depends on internal volume, voyage length and season, and the moisture held in pallets, cartons and the goods themselves. The quantity is calculated using the recognised desiccant-unit method rather than estimated, and for a full container of electronics it is normally measured in kilograms of calcium chloride, not a few silica sachets. Sealed barrier bags are dosed separately, against their own surface area.
Air freight shortens the exposure window and avoids salt-laden deck stowage, so it can be justified for commissioning-critical or high-value units. For volume shipments the more economical answer is usually a properly specified sea pack: barrier bags, a calculated desiccant load, under-deck stowage and a direct service. The comparison should include the cost of a delayed commissioning, not the freight rate alone.