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Red rust

We are producing precoated galvanized parts for refrigerators. These parts have to meet test ASTM B117 (salt spray test -- 500 hrs) because those parts have been sheared all the contour are exposed to corrosion. the thickness of the parts is 0.0165". Does anybody knows how to protect the exposed edges to avoid red rust during salt spray test?

BERNARDO PEÑA GONZALEZ
- MONTERREY, NUEVO LEON, MEXICO
2006

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Coat the edges with wax before subjecting them to salt spray test.

T.S.N. Sankara Narayanan
- Chennai, Tamilnadu, India
(ed.note: The good doctor offers a fascinating blog, "Advancement in Science" )
2006

The main property that has made galvanizing so broadly used for so long is that even when a small area of steel gets exposed, zinc takes care of the corrosion problem in a sacrificial way much like a battery. If you are experiencing rust on the edge maybe your zinc coat is too thin and the "battery" is getting exhausted before the test is over. Try increasing the zinc weight or thickness.

Guillermo Marrufo
Monterrey, NL, Mexico
2006