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Column 技術屋の解説

Column 技術屋の解説


[No.9/17] Basic knowledge of Anticorrosive polymer film (2)

In my previous column, I have explained that Kneaded type Anticorrosive polymer film is only available in the present market, although Coating type one is also there.

This time, let me continue again my explanation about the basic story of the anticorrosive polymer film.

Steel has been the main subject for most of anticorrosive polymer film.

The anticorrosive polymer film for other metals are also produced than steel.

The reason is that their demand is limited and very small, I can say.  

Probably, it may be the reason that the most descriptions of “anticorrosive polymer film” in pamphlets and technical data have been automatically directed for steel as if it had been a matter of course when they have picked up the subject of “anticorrosive polymer film”, without firmly specifying “for steel”.

As the target metal is the basic information when discussing the rust prevention technology, it is most regrettable for me that they have missed to specify clearly the target metal.

In addition, “Volatile anticorrosive polymer film” is the misleading name, although many manufacturers have been describing in their catalogs. Many of the rust preventive paper, which has been used long before anticorrosive polymer film introduced in the market, has been also called as “VCI paper”. The test to confirm “volatile corrosion prevention” is called as VIA (stands for vapor inhibitor ability) test, it is very severe test. It is the definite requirement for “VCI paper” to pass this test

However, most of “Volatile anticorrosive polymer film” so called products does not pass the VIA test. In other words, “Anticorrosive polymer film” is considerably weaker than “VCI paper” with regard to the volatile corrosion inhibiting ability.

I think anticorrosive polymer film had better be used with clear recognition of a risk, that it is inferior in volatile corrosion inhibiting ability than VCI paper, even though the product mentioned to have “volatile”.

Namely, it is very important point to ascertain of how much corrosion inhibiting  ability can be actually performed by the anticorrosive polymer film.

Of course, it is not wrong in Japanese to name as volatile anticorrosive polymer film in the meaning of which has “been volatile”. But, it is a problem what extent the film can exercise the volatile corrosion inhibiting ability.

The photo 1 show the results of investigation on what extent the volatile corrosion inhibiting ability has been actually performed for steel by VIA test.

8 types of kneaded type anticorrosive polymer film for steel in the market were the subject of investigation. As the rust can be seen evidently from these photos, any of the films is failing the test.

Incidentally, the rust has not occurred at all when the same test is performed with VCI paper.

Although volatile corrosion inhibiting ability is seen while weak in about half of the samples, which shows better results than the blank test (test in no corrosion inhibitor), almost half of the balance does not show any corrosion inhibiting ability as they are rusted to the same extent in the case of blank.

This is the actual situation of volatile corrosion inhibiting ability of anticorrosive polymer film.

VCI Paper                                Blank

Photo 1 : Volatile corrosion inhibiting ability when anticorrosive polymer film

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