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Temperature Performance

Unlike Hexavalent based passivation systems, TriPass coatings are capable of withstanding significantly higher temperatures without serious reduction in corrosion protection. This feature is due to the unique way in which the trivalent passivation film is formed, and the way in which the coating reacts to environmental variables like temperature.

The images opposite clearly demonstrate that TriPass does not dehydrate or crack in the same way that hexavalent films do, when exposed to elevated temperatures. This is because unlike hexavalent films, TriPass films contain almost no water after drying and thus do not desiccate during heating. This feature is more noticeable in hexavalent systems and temperatures as low as 60 degrees (C) can irreparably damage the passivation coating.

Electron-microscope images


Hex Pass - No Heating


Hex Pass - 120C / 1hr


TriPass - No Heat


TriPass 120C / 1hr

 


 



Conversely, rehydration of hex films can induce a limited amount of 'self healing' in areas of damage. This effect can be mimicked on TriPass films by the use of selected topcoats.

TriPass systems have been tested at temperatures of 120C for 4 hrs without significant degrading corrosion performance. If a topcoat is applied e.g. (TNT 15), corrosion performance is still reliable after exposure to temperatures of 150C for 24 hrs.

TriPass films and Torque N Tension top coats work synergistically to increase corrosion resistance. Testing has repeatedly demonstrated that this combination can out perform alloy coatings like zinc-nickel at a significantly lower cost.