Sti-P3, Act-100 Composite Tanks - Double and Single Walled Sti-P3 Tanks Cathodically protected tanks with hard, epoxy outside coating and zinc anodes installed to combat electrolisis  Act-100 Composite "Glasscote" Tanks Same basic construction as Sti-P3 tank, but with 100 mil coat of chopped fiberglass. No anodes are attached to these tanks.