Humidity will kill the adhesion through formation of iron oxides (rusting).
I'm basing my comments on my tyre development experience. In tyre skim compounds for brass-plated steel cords there are no alkaline metal oxides or hydroxides used. The adhesion layer is copper sulphide rather than zinc sulphide.
The surface chemistry of carbon black is basic (alkaline) with a pH = 8 or 9; the usual accelerator (DZ) is also basic in nature. SiO2 has an acid surface chemistry - pH about 4 or 5.
it's true that "the adhesion layer is copper sulphide rather than zinc sulphide" but I found in literature data about a curative interaction between CuII ZnO accelerator sulfur and stearic acid (van Ooij;Tsai;Chandra)
