This specification covers several different types of chemical passivation treatments for stainless steel parts. The treatments are the following: immersion treatment using nitric acid solutions, immersion treatment using citric acid solution, and electrochemical treatment. Immediately after the removal from the passivating solution, the parts shall be thoroughly rinsed, using stagnant, countercurrent, or spray washes, singly or in combination, with or without a separate chemical treatment for neutralization of the passivation media. The chemical reactions of the passivating media on the surface of the stainless steel shall be stopped by rinsing of the stainless steel part, with or without a separate neutralization treatment. A chemical treatment shall be applied which will accelerate the formation of the passive film on a chemically clean stainless steel surface. The passivated parts shall exhibit a chemically clean surface and shall, on visual inspection, show no etching, pitting, or frosting. The following tests shall be performed on each lot of stainless steel parts: water immersion test, high humidity test, salt spray test, copper sulfate test, and potassium ferricyanide-nitric acid test. A free iron test shall be used for the detection of free iron on the surface of stainless steel.
1.1 This specification covers several different types of chemical passivation treatments for stainless steel parts. It includes recommendations and precautions for descaling, cleaning, and passivation of stainless steel parts. It includes several alternative tests, with acceptance criteria, for confirmation of effectiveness of such treatments for stainless steel parts.
1.2 Practices for the mechanical and chemical treatments of stainless steel surfaces are discussed more thoroughly in Practice A 380.
1.3 Several alternative chemical treatments are defined for passivation of stainless steel parts. Appendix X1 gives some nonmandatory information and provides some general guidelines regarding the selection of passivation treatment appropriate to particular grades of stainless steel. It makes no recommendations regarding the suitability of any grade, treatment, or acceptance criteria for any particular application or class of applications.
1.4 The tests in this specification are intended to confirm the effectiveness of passivation, particularly with regard to the removal of free iron and other exogenous matter. These tests include the following practices:
1.4.1 Practice A - Water Immersion Test,
1.4.2 Practice B - High Humidity Test,
1.4.3 Practice C - Salt Spray Test,
1.4.4 Practice D - Copper Sulfate Test,
1.4.5 Practice E - Potassium Ferricyanide-Nitric Acid Test, and
1.4.6 Practice F - Free Iron Test.
1.5 The values stated in inch-pound units are to be regarded as the standard. The SI units given in parentheses are for information only.