Summary for magnesium fluoride passivation Discussion
Magnesium fluoride / sodium tripolyphosphate passivation is the key concern in this thread: Stephen Landers asks whether a proposed chromium-free treatment for pre-galvanized sheet steel will still allow neutral-cure silicone sealant and acrylic-PSA sealing tape to adhere. He lists a fairly aggressive formulation containing magnesium fluoride, sodium tripolyphosphate, fluorozirconic acid, sodium fluoride, hydrochloric and nitric acids, phosphoric acid, vinyl triacetoxy silane, sulfuric acid, calcium nitrate, and water. The excerpt provided contains only the question, so no answerer’s guidance or final verdict is shown. As a result, the page centers on whether this passivation chemistry may interfere with bonding performance, but the actual outcome is not available in the supplied text.
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