Purpose

This specification establishes the requirements for etch inspection of bare high-strength low-alloy steel parts having tensile strength of 180 ksi (1241 MPa) and higher and of carburized parts to detect overheating caused by abusive machining or grinding in the heat treated condition, and to detect localized discontinuous carburization. This process is not applicable to surface hardened steels produced by nitriding or carbonitriding. This process may remove 0.0001 to 0.0005 inch (2.5 to 12.7 micrometers) from the surface of the part.

Classification

Etchants used in this specification are classified as follows:

Type 1 - Nitric acid in water or alcohol with an anti-smut additive

Type 2 - Nitric acid in water or alcohol

Type 3 - Ammonium persulfate in water

Type 1 and Type 2 etchants may be used interchangeably. Type 1 immersion or Type 3 swabbing method shall be used when the part cannot be hydrogen embrittlement relieved.

Type 3 etchant shall be applied by swabbing and only used when authorized by the cognizant engineering organization. Type 3 is not as sensitive for detecting grinding burns as Type 1 or Type 2.

Safety - Hazardous Materials

While the materials, methods, applications, and processes described or referenced in this specification may involve the use of hazardous materials, this specification does not address the hazards that may be involved in such use. It is the sole responsibility of the user to ensure familiarity with the safe and proper use of any hazardous materials and to take necessary precautionary measures to ensure the health and safety of all personnel involved.