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Magnesium fluoride / sodium tripolyphosphate passivation: will tape and silicone adhere?

December 1, 2015

Q. Good morning,

I'm reviewing a proposed passivation treatment for pre-galvanized sheet steel. The fabricator would like to use a chromium-free coating. I'm wondering whether this treatment will prevent us from successfully adhering silicone sealant (neutral cure) and sealing tape (with an acrylic PSA). Here is the formula of their passivation treatment:

Component feeding amount (g / L)
98 to 100 of magnesium fluoride
Sodium tripolyphosphate 10 to 30
Fluorozirconic acid 10 to 30
Sodium fluoride 23 to 25
Hydrochloric acid and 45 to 46
Nitric acid 10 to 30
Phosphoric acid 100 to 120
Vinyl triacetoxy silane 10 to 30
Sulfuric acid 30 to 40
Calcium nitrate 30-50
Water Balance

Thank you all

Stephen Landers
- Long Beach, California, USA

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