(R) Plating, Cadmium (Electrodeposited)
|Publication Date:||1 March 2021|
This specification covers the requirements for electrodeposited cadmium plating.
The electrodeposited cadmium platings covered by this specification are intended for use as corrosion protective coatings. Unless otherwise specified, components heat treated to an ultimate tensile strength greater than 200 ksi (1379 MPa) or harder than 43 HRC should not be plated in accordance with this specification. Section 5 contains more information about the appropriateness of this process and the coating material. It also describes alternatives to cadmium plating.
Cadmium plating shall be of the following types and classes, as specified (see ordering information):
I - As plated
II - With supplementary chromate treatment (see 220.127.116.11 and 18.104.22.168) Grade A - Hexavalent chromate treatment, maximum service temperature 250 °F (121 °C) Grade B - Hexavalent chrome free treatment, maximum service temperature 375 °F (191 °C)
III - With supplementary phosphate treatment (see 22.214.171.124)
For Type II plating, if no grade is specified, Grade A shall be supplied. Processors shall have the option to use Grade B if permitted by the cognizant engineering organization.
Type II, Grade A may be listed as Type IIA and Type II Grade B may be listed as Type IIB; the terms are equivalent.
1 - 0.0005 inch (0.0127 mm), minimum
2 - 0.0003 inch (0.0076 mm), minimum
3 - 0.0002 inch (0.0051 mm), minimum
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 which 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.
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... View More
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.
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.
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 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.View Less