Electroplating process schematic
Electroless nickel process schematic
qualification by the MIL-DTL-38999 specification is expected to result in increased adoption of tin-zinc in the aerospace and military industries, as well as other industries where high-performance coatings are required. Overall, the qualification of tin-zinc by the MIL- DTL-38999 specification is a positive development for the aerospace and defense industries, and demonstrates the growing confidence in tin-zinc as a replacement for cadmium in high-performance applications. Is Tin-Zinc applied in an electroplating or electroless plating process? Tin-zinc is typically applied through an electroplating process. In this process, a layer of tin and zinc is deposited onto the surface of the substrate through the application of an electrical current. The electroplating process for tin-zinc typically involves several stages, including surface preparation, activation, plating, and post-treatment. During the activation stage, the surface of the substrate is treated to increase its reactivity, allowing for better adhesion of the tin-zinc coating. In the plating stage, an electrical current is applied to the substrate, causing the tin and zinc to be deposited onto the surface. Finally, the post-treatment stage may involve processes such as passivation, to improve the corrosion resistance of the coating. In comparison, electroless plating is a process in which a metal coating is deposited onto the surface of a substrate without the use of an electrical current. Electroless plating is typically used to deposit uniform, consistent coatings onto complex
or irregularly shaped surfaces, and is not commonly used for tin-zinc plating.
You mentioned compatibility with other materials. Would a Tin-Zinc plated part be galvanically compatible for combined use with older cadmium-plated parts? Galvanic compatibility refers to the potential for corrosion between two dissimilar metals when they are in electrical contact with each other in the presence of an electrolyte (such as salt water). When two dissimilar metals are in electrical contact, a galvanic cell is formed, and the metal with the more negative electrode potential corrodes preferentially. Tin-zinc and cadmium are dissimilar metals, but combining them in a galvanic couple does not necessarily result in corrosion of one of the metals, as the two sacrificial components (zinc and cad) are approximately next to each other on galvanic index tables. Depending on the electrolyte and the relative electrode potentials of the two parts, little or no dissimilar metal corrosion may occur. Overall, the extent of galvanic corrosion between tin-zinc and cadmium depends on several factors, including the specific electrolyte, the temperature, the concentration of the electrolyte, and the relative surface areas of the two metals. To minimize the risk of galvanic corrosion, it is always important to use suitable corrosion-resistant materials and coatings, and to consider factors such as the design and construction of the components and the environment in which they will be used. Ultimately, it is the responsibility of SAE and other certification agencies to determine mating compatibility of dissimilar components.
QwikConnect • April 2023
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