SAE規格 AMS-QQ-P-416 Revision G, 2022, Plating, Cadmium (Electrodeposited)

Description

- General Usage: Processes used for cleaning and cadmium deposition on components heat-treated to, or having ultimate tensile strength of 152 ksi (1048 MPa) or higher tensile strength or 34 HRC or higher, should incorporate practices and procedures to minimize hydrogen embrittlement.
- Limitations
- Temperatures: Cadmium plating should not be used on components for space applications, high vacuum applications, or on components that in service reach a temperature of 450 °F (232 °C) or higher or come in contact with other components that reach those temperatures. Cadmium plating should not be used on titanium components, and cadmium plated components should not be used in contact with titanium components.
- Plating of Internal Diameters: When process limitations will not allow cadmium to be deposited on internal diameters that require corrosion protection, an alternative method of protection should be specified. For example, it is difficult to obtain complete plating coverage in areas beyond a hole depth of 2.5 times the hole diameter for holes equal to, or smaller than, 0.75 inch (19 mm) in diameter unless special fixturing is used.
- Mechanical Deposition: To avoid problems of hydrogen embrittlement on hardened steel components, such as chains and springs, it may be helpful to use the mechanical deposition method of cadmium plating. (This process is covered in AMS-C-81562 and ASTM B696.)
- Type II Treatment: The prime purpose of Type II treatments on electrodeposited cadmium plating is to retard or prevent the formation of white corrosion products on surfaces exposed to stagnant water, high humidity atmosphere, salt water, marine atmosphere, or cyclic condensation and drying. Type II treatments are preferred for components that will not subsequently be completely coated. The Type IIB treatment was added to allow treatments that are required to meet Registration, Evaluation, Authorization and Restriction of Chemicals (REACH) requirements for manufacturing or importation into the European Union.
- Type II Temperature Limitations: Chromate treatment (Type IIA) should not be used on plated components that will not be coated and that will be continuously exposed to temperatures in excess of 150 °F (66 °C) or intermittently exposed for short periods to temperatures of approximately 300 °F (149 °C) or more. However, this treatment may be used to prevent finger marking and corrosion which may occur at room temperature during assembly and storage.
- Type II Handling Precaution: Type II supplementary coatings which involve only dipping in chemical solutions, normally require a sufficient period of drying, approximately 24 hours at 70 to 90 °F (21 to 32 °C), to render the components suitable for handling without damage to the coating while in gelatinous forms. It is important with such coatings that the workmanship be such that the coating is not excessively damaged while wet. Type IIA and Type IIB treatments should be dried for 24 hours before painting.
- Type III Treatment: The prime purpose of Type III phosphate treatment on electrodeposited cadmium plating is to form a coating base. Because of the enhanced adhesion properties, the phosphate finish is preferred for components that will subsequently be completely coated.
- Brighteners: Brighteners are organic or metallic compounds that, when added to alkaline cyanide cadmium plating baths, influence the formation of the electrodeposited cadmium crystals.
-Tensile Strength and Hardness Values: The heat treated material tensile strength and hardness values as specified in this document represent the minimum values specified in the procurement specification or end product drawing. They do not represent the values obtained from actual hardness or tensile testing of the component, or calculations of tensile strength based on actual tested values and various stress areas.