Abstract: An ammonium polyphosphate based fire-retardant composition comprises an ammonium polyphosphate, a suspending agent, and an effective amount of at least two corrosion inhibiting agents selected from the group of corrosion inhibiting agents including activated carbon, Epsom salts, Gypsum, azoles, and vapor phase inhibitors. The composition may further include a xanthan gum, a coloring agent or both. TABLE 1 Formulation in Weight % Formu- Formu- Formu- Formu- Formu- Formu- Component lation 1 lation 2 lation 3 lation 4 lation 5 lation 6 Ammonium 91.80 91.80 91.75 90.80 91.80 91.75 Polyphosphate Attapulgite 1.50 1.50 1.50 1.50 1.50 1.50 Clay Iron Oxide 1.20 1.20 1.20 1.20 1.20 1.20 Xanthan Gum 1.30 1.30 1.30 1.30 1.30 1.30 Epsom Salt 0.10 0.10 0.15 0.10 0.10 0.15 2-mercapto- 0.10 0.10 0.10 0.10 0.10 0.10 benzothiazole Benzotriazole 1.00 2.50 2.50 2.00 2.00 2.00 VpCl-609?™ 2.00 1.50 1.50 2.00 — — Ammonium — — — — 2.00 2.