CAUTION. CARBON TETRACHLORIDE SHALL NOT BE USED AS A SUBSTITUTE FOR CLEANING SOLVENT. 3-11. SLUDGE, Sludge is formed by accumulations of coolants, cutting oils, metal turnings, dirt, previously used lubricants, water, and various other foreign matter. Accumulations will vary in consistency from liquids to hard, dense deposits, and may be either or both acid-or-moisture-saturated. Etching properties of these deposits result fram the presence of acid and chlorinated cutting oils. Oxidation or the action of corrosion is attributable to the presence of high-moisture-content coolant solutions, condensation action, accumulation of moisture fran exposure in shipment, and outdoor storage. The condition is aggravated where deposits are impacted with metal turnings around-critical opera-~ ting mechanisms, such as spindles, bearings, bushings, tool drive sys- tems, etc. When flushing operations with rust-inhibiting oils, detergents, steam cleaning, or solvent-wash methods fail to remove dense sludge deposits, it will be necessary to employ nommetallic brushes and scra- pers. 3-12, RUST REMOVAL, Rust or any form of oxidation shall be removed frm critical working surfaces. The nature of the operation involved will vary in control requirements from those essential to maintain operational limits of critical pieces, to such simple operations as the removal of incipient rusting from noncritical pieces by normal cleaning. observed on critical operating surfaces shall be removed. 3-13, Rusting Rust removal may be accomplished by the use of phosphoric-acid type rust remover (hot bath or local application), vapor blast with rust- inhibited liquid vehicle, buffing, nonmetallic brushes. Where only inci- pient rusting exists, vapor degreasing units or solvent wash methods may be used. CAUTION, METALLIC BRUSHES AND ABRASIVES SUCH AS EMERY PAPER, FILES, AND SAND BLASTING SHALL NOT BE USED ON CRITICAL SURFACES, 3-14. When phosphoric-acid type rust removers are used, a rinsing and neutralizing bath shall follow. The bath shall be cold water with continuous feed and drain. A second bath may be applied at a temperature of not less than 1800°F, to aid in drying of the treated parts. The second bath shall contain 8.5. ounces of chromic acid for each 100 gal- lons of water. This is not a costly bath and shall be renewed daily where used. Where local application of phosphoric-acid type rust remover is made, neutralization shall be accomplished with water-—dampened rags, and the parts or assemblies shall be dried immediately. Dry rags, infra-red banks, dry-campressed or other motivated air may be used for drying operations. Grease ami oil accumulation shall be removed from 18-29