About K4M8 What is K4M8? K4M8 (K Formate, Potassium Formate, HCO2K, HCOOK, or CHKO2, is the potassium salt of formic acid. Four elements: potassium, hydrogen, carbon, oxygen.Bactericidal at operational concentrations.Fully biodegradable upon dilution.No halide ions present.No environmentally persistent chloridesNo Chloride Stress Corrosion Cracking (CLSCC) The K4M8 Premise K4M8 (potassium formate brine) is a cost-effective superior replacement for most viscosified solids-laden drilling fluids under 13.1 lbs/gal (1.57 SG)