General: The vacuum deposited cadmium coatings covered by this specification are intended for use as corrosion protective coatings on ferrous parts. Because of application procedures used, such parts are free from hydrogen contamination and resultant hydrogen embrittlement thereof. Cadmium deposition by vacuum technology is recommended to be used on steels heat treated to or having an ultimate strength of 200,000 psi or above (approximately Rockwell hardness C 43) rather than electrodeposited cadmium plating in accordance with QQ-P-416.
Type II treatment: The prime purpose of chromate finishes (Type II) on vacuum deposited cadmium coatings is to retard or prevent the formation of white corrosion products on surfaces exposed to stagnant water, high humidity atmospheres, salt water, marine atmospheres or cyclic condensation and drying. Some types of chromate coatings have proved satisfactory as a base for paints.
Type III treatment: The prime purpose of phosphate finishes (Type III) on vacuum deposited cadmium coatings is to form a paint base.