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Paint adhesion spec help needed.

UKCMM
We have a requirement to test painted parts to MIL-DTL-53072 and have only got an issue C copy latest I believe is issue E .

The area of concern is section 4.2.3.6.1 Dry adhesion assessment our copy states 3 or more squares are a failure our customer
is saying 4B or better IAW ASTM D3359 can anyone confirm this change.

Thanks
  • We have a requirement to test painted parts to MIL-DTL-53072 and have only got an issue C copy latest I believe is issue E .

    The area of concern is section 4.2.3.6.1 Dry adhesion assessment our copy states 3 or more squares are a failure our customer
    is saying 4B or better IAW ASTM D3359 can anyone confirm this change.

    Thanks

    I can't help with the MIL spec, but I do have a copy of ASTM D3359-09 that came with a Gardco adhesion test kit. There is no mention of what is or is not a failure, but there is a table for the classification based on percent, and 4B is one of the classifications - less than 5%, it looks to me like a small portion of 4 of the squares has peeled, but as I understand this is about the percentage of the whole rather than the number of individual squares affected. There is also a lot of text about a tape controversy due to the tape previously specified no longer being available and full testing of the suggested replacement tape not yet concluded. And there are rules for square spacing based on coating thickness.

    My advice is that if you are required to test and report to a specification you need to buy a copy of the current spec. I am attaching an image of the ASTM D3359 classification chart.

    HTH


  • This is an excerpt from MIL-DTL-53072E Para 4.2.3.61:

    4.2.3.6.1 Dry adhesion. Perform the adhesion test in accordance with ASTM D3359, method B,

    cross cut tape adhesion, using the 6-line pattern and 2 mm (0.079 inch) spacing. Any

    commercially available tape (1 inch width) that will yield a minimum of 80 oz of adhesive

    resistance over the tested coating when tested in accordance with ASTM D3330/D3330M shall

    be used. The assessment of the adhesion of the coating film shall be determined by its ability to

    not peel when tested in accordance with ASTM D3359. The resultant test rating shall be

    classified as scale 4B or better. Where CARC dry film thickness has exceeded 7 mils (175

    microns), method A of ASTM D3359 shall be used, if permitted by the procuring authority. The

    resultant test rating, if using method A shall be classified as scale 4A or better. The scribed area

    shall be repaired in accordance with the procedure established in 3.6.1 and 3.6.2. Rejected items

    shall be reworked in accordance with 3.6.

  • Thanks for the help with this I have just requested a copy. Painting is not the sort of thing we normally get involved with, but to get this contract we had no choice.
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