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Wet Sponge porosity holiday Test, is a Dinosaur - Video


Wet Sponge Test, do we need to say goodbye to this, as it is a Dinosaur, for the coating specifiers.


View our video about the history of wet sponge testing


Low voltage wet sponge testing—should we be saying goodbye to this dinosaur?

I know that I said should we be saying goodbye to this dinosaur? What I should have said is we should be saying goodbye to this dinosaur of a test.

With advances in electronics and high voltage DC detectors, the wet sponge tester test has become a dinosaur.

The latest high voltage DC porosity / holiday detectors

PCWI Porosity Holiday Detectors we make a vast range of brass brushware and coils to suit these instruments all makes and models.

You should have seen the previous video called low voltage wet sponge testing its use and its history and then come back to this one.

Flaws commonly found in coating systems

Although the electronics are the latest the concept of the test is not. With wet sponge testing you can see here a vast amount of differing flaws in a coating. A low voltage wet sponge test would only find flaw number one. That would also be dependent on the flaw's diameter, coating thickness and the flaw's capability of being wetted out.

So why would you specify a wet sponge test? It is slow to use, it is a wet test and you can only find a flaw exposing the actual substrate. You could do the test with high voltage DC porosity holiday detector set low as a dry test and find most if not all of those flaws and get coating longevity.

Statements being made by some about the wet sponge units capabilities are totally incorrect. The wet sponge test cannot find what we would consider to be a flaw in the coating. The wet sponge unit can only find one type of flaw and that flaw must also be able to be wetted out. Fine pin holes may not wet out very well. Flaws must also have the bare substrate actually exposed in order for this unit to complete the electrical circuit to sound the alarm.

Latest wet sponge detector. Modern units - out of date test

Some reasons why the low voltage wet sponge test still exists:

  1. Because of long running miss information about the high voltage DC detectors and the damage that they may cause on the thinner films
  2. Because of the lack of knowledge, information about the advances in electronics in the latest DC detectors. Especially constant current enabling testing of very low voltages.
  3. Standards are lagging behind the latest technology. Industry's lack of communication with standards committees.
  4. Coating specifiers, lack of knowledge or not being informed although they tend to work with set standards. Standards do allow for high voltage DC testing of films of a hundred and fifty microns and up.
  5. Wet sponge testing equipment can be purchased at a much lower cost. Although the test takes much longer to do making the testing more expensive overall.

So why is it then a standard states that you can test the thin film of a hundred and fifty microns and up with high voltage DC detector yet we find the wet sponge test still being specified and then even up to five hundred microns and beyond.

A little note here: should you decide to use a high voltage DC detector, not a pulse DC detector, make sure the probe that you use is a fine bristle brass wire brush do not use a carbonised rubber neoprene probe. Why?  Watch the video Porosity Holiday Testing you need to know this to learn more.

I’d like to make a recommendation, take a look at the relevant videos that we have published here on our website on porosty testing. Then you'll be in a position to make up your own mind.

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