GFS Tank — Glass-Fused-to-Steel Bolted Storage That Stays Corrosion-Free for 30+ Years When a storage tank sits in wastewater, biogas slurry or seawater, paint and concrete both fail. A GFS tank fuses glass directly to steel, so the surface that touches your liquid is inert, seamless and permanent. No repainting. No cracking. Just decades of service. A GFS tank (Glass-Fused-to-Steel tank) — also called a glass-lined steel (GLS) or enamel bolted tank — is the storage vessel