This issue is resolved in a couple of ways in 2018 sp01.
1. All SW decal mapping modes import into Visualize as of 2018 sp01.
2. Faces with decals in SW, are automatically broken out into their own Visualize parts.
You should be able to manually resolve this in 2017 by extracting the outer cylindrical face as it's own part in Visualize, then apply the decal again in Visualize. To do the part extraction I recommend switching the viewport to "Preview" mode. Then while in part selection mode, right click on the face and choose Extract Part... Select the face again and use the slider so it only highlights the triangles on the outer cylindrical surface... or at least enough of it to map your decal onto. Then re-apply the decal. NOTE you might have to delete the decal, as once you split the outer surface, the mapping of the current decal will be fubar. Simply delete it from the appearance tab, right click and choose new decal, then import it again, drop it on the (newly extracted) part and size/position accordingly. Then the decal will only display on that surface.