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topic 8583

Rust Spot Due to "Sweating"!


We manufacture electric resistance welded (ERW) and cold drawn electric resistance welded (CDW/DOM) tubing in India and exporting worldwide. We pack the tubings using HDPE sleeves. Some of our customers noticed rust spots on the tubing, which they call as "sweating". The average transit time is 4 weeks thru sea route. I would like to know the reason behind this.

- Chennai, Tamilnadu, India


If the parts are packaged under ambient shop conditions you are probably experiencing a dew point problem.

When the package is sealed, the ambient air is trapped inside. When the temperature during shipping drops below the wet bulb temperature, moisture will condense out of the air inside the package. That is your sweating.

That is why many items shipped to the U.S. are packaged with a small package of desiccant, or some other means of absorbing the moisture within the package.

Kelly Loch
- Syracuse, New York


Dear Kelly Loch,

Let me thank you for your feedback on my question about"sweating". yes! as you rightly said , we have used "solica gel" to avoid such rust stain problems... is there any other method available.. can we do something with the rust preventive oil we apply on the tubes before shipping?

kindly advice.... I once again thank you ... regards,

- Chennai, Tamilnadu, India


Shipping thru a sea route exposes your product to high humidity and salt. You may try some type of VCI protection. VCI is vapor corrosion inhibitor. We may use paper or plastic which has been treated with VCI. It increases our packaging costs. We use it when it effectively reduces claims associated with transportation rust and/or sweating. The distance you are shipping, may force you to improve your packaging.

Are your tubes shipped inside large rectangular trailers or containers ? If so, they may be protected from direct contact with salt spray, but not water. I've unloaded containers like this. It will actually rain inside them. Water condensates on the inside roof and rains down on the contents of the container.

Paper or plastic with VCI protection may eliminate your sweating problem. Presently, may integrated steel manufactures wrap steel coils in plastic VCI film. This protects the coils from sweating and other damages during transportation.

We use large plastic tubes, treated with VCI, to ship smaller coils. The coil is inserted into the tube. The ends of the plastic tube are tucked into the inside diameter of the coil.

Perhaps you can use some type of VCI paper or plastic to wrap your tubes ? Good luck.

Terry T. Magyar
steel co. - Gahanna, Ohio


Dear Mr.Terry T Magyar,

Kindly accept my thanks for your detailed feedback on my question about "sweating" based on your suggestion we could able to locate a VCI coated sleeve manufacturer in India and we are trying out with this sleeve for the current shippings to USA and Canada.

I once again thank you for your suggestion...

With best regards,

- Chennai,Tamilnadu,India

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