Metal finishing Q&As since 1989

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Plating problem?

2003

We export steel parts that are yellow passivate zinc plated and these parts have finishing problems upon arrival at our customer premise. These parts are packed in boxes with bitumen sheets on the inside of the box. The shipment transit time is about 30-35 days in 20' container, from the north down (0 degree C) to the south (up to 40 degree C - inside the container)and up north again. When my customer opens up the boxes of parts, condensation (in the form of water droplets) are obvious on the parts and parts have signs of powdery surface and rust at joints. What could have cause these problems and how to prevent future occurrance?

G. P. Lim
- Singapore

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As no else has attempted to answer I will try. As you state there is condensation showing on opening, then your parts are in a state of 100% humidity which on cooling is condensing.Storing in 100% humidity or with condensation will cause corrosion.If you must store in completely sealed containers I think you will need to store with a lot of dessicant to absorb the humidity/moisture. Air at high humidity at 40oC holds a lot of moisture.

Geoffrey Whitelaw
- Port Melbourne, Australia
2003

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I know of a similar problem which occurred with a manufacturer shipping electronic enclosures out of Malaysia. One question is did this problem just start occurring or has it always been a problem? If it's a new problem, review any changes to the finishing, packaging, and shipping processes (as Mr. Whitelaw suggested), if it's an old problem, review the finish specifications and make sure that they are adequate for the intended use of the product.

In the case I mentioned, the electronic enclosures were intended for office use and the most severe exposure to corrosion occurred during shipping. As it turned out, the finishing specs were beefed up to meet the relatively short shipping and storage requirement and not for the long term office exposure.

Michael Wisniewski
- Chatsworth, California, USA
2003