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Column 技術屋の解説

Column 技術屋の解説

2016.08.02

[No.15/17] How to use VCI paper correctly No. 2

Let me explain about “How to useVCI paper correctly” following the last time.

I picked up it last time as an error, which can be seen when VCI paper used, that the target metal has not been firmly confirmed.

 Then, a common mistake is in the case that there is something between VCI paper and the target metal. Although VCI has volatile property literally in VCI paper used, it would no longer be able to reach the metal surface if there is anything.

Let me talk from the case that seems to be most often seen.

It is the lack of cleaning of the metal to be packed. VCI can never be directly absorbed to the metal surface unless all the dirty material has been well removed from the surface. The VCI can be absorbed only on the dirty material surface.

Even if carefully packaging with VCI paper, there is a possibility that the rust occurs in the case the dirt remains on the metal.

If the target metal is covered with any dirty material with a corrosive substance, you are forced to understand the metal will be certainly rusted.

 The most familiar corrosive material is the workers’ perspiration and sebum. If they remain on the metal surface, the target will be certainly rusted. Cleaning is indispensable before packaging with VCI paper.

 Now, let me explain that the expected effect cannot be obtained when used in the wrong way, even after properly the cleaning conducted. Here is the extreme example.

 In the case that you use VCI paper for the target metal in the plastic bag, you must either wrap the metal by picking up from the plastic bag or put VCI paper also in the bag. Nobody can get any corrosion preventive effect, even if wrapped with VCI paper from outside of the plastic bag.

 Although it is not so much extreme, but it can be seen well that many customers try to wrap the target metal, which has been coated with rust preventive oil, with VCI paper.

It is the same as the previous extreme example. The VCI(volatile corrosion inhibitor) vaporized from VCI paper, cannot touch the metal surface coated by the rust preventive oil. The VCI may work on the metal surface, to be coated by rust preventive oil, only where the oil is not unintentionally coated.

 In other words, you cannot expect any further effect enhanced for the metal which the rust preventive oil has been properly applied, even with VCI paper. You should not easily expect the combined action of rust preventive oil and VCI paper.

 However, it is also a fact that there is a worthy effect, when the target metal, coated with rust preventive oil, is packed with VCI paper.

 Maybe then, some of oil might not be coated on the said place, VCI paper might have had a protective effect on the oil-coated surface. In the latter case, you will not need to dare use VCI paper. It should be judged on a case-by-case, and you should verify whether there was an effect for any reason. Otherwise, a wasteful application may be continued.

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