MIL-STD-865D
used provides they meet the applicable plating requirements and are qualified by procedure tests. However, plating and preparatory solutions of different manufacturers should not inter-mixed or substituted into a plating procedure.
4.2.2 Characteristics of selective plating solutions. The solution manufacturers have pre-cared and made available comprehensive literature on their solutions. This information should be reviewed when selecting a solution and the instructions followed when using the solution. The solution containers are labeled as to range of voltage
for various anodes and solution factor. This information should be used during plating operations. The selective plating solution characteristics listed in the Appendix are presented as a guide for solution selection and use.
4.2.2.1 Solution usage.
a. Alkaline and neutral solutions are preferred on porous base metals, white metals, high strength steel and for improved throwing power.
b. Acid solutions are generally used for rapid build-up and as a laminating structure material in conjunction with alkaline type solutions.
4.2.2.2 Immersion deposits and pre-plates. Immersion deposits will formed by certain solutions on certain base materials when pre-wetting a surface with no current flowing. Immersion deposits have poor adhesion to the base materials. Pre-plates are often used to prevent immersion deposits from forming thereby improving adhesion. Common pre-plates are nickel, gold and palladium. When plating with solutions that form immersion deposits, care must be taken to avoid any solution contact with the part prior to plating. Solution literature generally is a good guideline on what solutions form immersion deposits.
4.2.2.3 Chrome plating solution. Chrome deposited from selective plating solutions is not recommended as a wear resistant coating. The hardness of selective brush plated chromium deposits is about 600 Brinell as compares to 1000 Brinell for hard chrome deposits from a tank. In addition the limited thickness and difficulty of producing sound deposits from selective chrome plating solutions result in the use of other metals such as nickel or cobalt in applications, which chromium would normally be used.
4.2.2.4 Build-up. Brush plating solutions are limited in the thickness that can be deposited since the deposit surface at some point becomes excessively rough. The thickness at which deposits become rough varies from 0.001 to .0030 inches but as a general rule the average is 0.005 inches. At this point for higher build-up, the deposit must be smoothed by machining, grinding, or sanding. The deposit must then be cleaned, etched and reactive before additional material can be applied. This can be easily and reliably done on more noble metals such as copper acid deposits, silver, gold, etc. The harder materials such as cobalt and nickel tend to form passive films and must be activated; an operation that requires speed and operator skill, this presents some element of risk. There several techniques to circumvent this element of risk, they are:
a. Select metals and/or specific solutions with less of a tendency to become rough with thickness. The manufacturers of selective plating solutions have developed several solutions specifically for heavy build-up. By supplying these solutions
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