Prior to Nitrox/O2 usage, visibly dirty or rusty dive tanks require abrasive tumbling prior to any degreasing treatment. Tumbling with ceramic media and citric acid (citrate) cleaner usually gives excellent results. Citrates are widely used in the metal finishing and electronics industries for oxy-cleaning processes; they are completely non-toxic, unregulated substances. Global cleaner is diluted 1 oz. per gallon of water for actual use.