penetration by glue into the coating

[anne]

Hello, i need an opinion about BST, how deep can penetrate the glue into the coating? The metalic coating manufactured by plasma or hvof (dense with max. porosity 5%). I wonder about the legitimacy of testing the coating with thickness about 150-200um. Is it possible that the glue can penetrate until the base material? In my opinion is not possible, but i've met with different opinion. Additionally i need to understand how deep can penetrate the sealant, for example METCOSEAL.

Best regards,

[Vig]

Anne,
Plasma and HVOF are quite different coatings.
Pores in the plasma coating will be interconnected in most of the cases. Could glue penetrate 150 mkm deep?
Normally - no. You could see the level of penetration in some microstructures, and it is not deep.
HVOF coating will have as-sprayed porosity at the surface level, but good HVOF or HVAF coating will have close to zero porosity below.
So you will not have a chance to reach the substrate with a glue.
There is an instrument to test gas permeability of different coatings, which could help to predict possible level of sealant penetration (and possible corrosion and wear resistance!) http://www.kermetico.com/equipment-gastest.php
Regards,
Vitaly

[anne]

thanks a lot! I have one more question. The same coating sprayed with the same parameters in the same condition, but with different thickness (for ex. 0,2mm and 2 mm) should have the same bond strength? Regards