[No.12/17] Considerations when using anti-corrosive polymer film
Up to the previous columns, I have continued my story of anticorrosive polymer film by highlighting its performances, and therefore I hope you can get what quality and features it has. This time, let me focus on the things that have to be careful when using it.
In 9th column, I emphasized that anticorrosive polymer film is weak in terms of volatile corrosion inhibiting ability. Therefore, it is advised to quit using the film away from the metal because of this nature.
It is a limited way for corrosion inhibiting materials that have firm volatile corrosion inhibiting ability such as the way to make the packaging inside an atmosphere of the corrosion inhibitor by putting metallic products together into plastic bags and containers etc.
Please always try to use general anticorrosive polymer film by making it contact with the metal as much as possible. And, it is important to seal tightly with heat sealing etc. It is not the best packaging to wrap with “furoshiki” cloth and to pack caramel those are creating gaps when only taped after overwrapping.
If there was gap, it may corrode the metal that the outside moist air and the condensed water outside the packaging would enter into and through the gap between.
As the torn or perforated packaging is so prone to fatal, it will require attitude to consider carefully the packaging system such as not to tear during transportation, working procedures and shipping method. I think it would be necessary several times efforts than using VCI paper for the above careful consideration and behavior.
Another concern will occur in the case that the remaining amount of air is much inside the pack, even if it is possible to have a perfect seal. It happens when the humidity in the air, taken into the internal pack, is high. The condensation occurs when the high humid air is cooled, but the condensed water cannot escape to the outside of the package because of the film and it will be confined within the package. The metal may be prevented from rusting once corrosion inhibitor solved into the condensed water to some extent, but the corrosion will occur due to the water if its corrosion inhibitor concentration is low. The environmental humidity when packaging is high, the rusting risk increases. It is the key that how much corrosion inhibitor gets melted from anticorrosive polymer film and what volume the condensed water is.
Another, there is a case that requires attention. There is a possibility that occurs when anticorrosive polymer film is in close contact with the metal. As the air flow is stopped when the film is in close contact with the metal, there is a risk of creating oxygen concentration cell which may cause the corrosion. As the contact degree may be changing by the packed metal weight, the probability of rust occurrence will become higher as the heavier metal.
I have firstly talked it is important to be contacted as possible, but we should avoid close contact with, namely subtle control will be required.
By the way, I think it rarely generates oxygen concentration cell in the case of VCI paper which is in close contact with the metal, because the VCI paper is porous.
As there are several points to pay attention, I think it is important to use anticorrosive polymer film after fully understanding on the abovementioned.