Description

Although there are acceptable substitutes (e.g. ZnNi), cadmium coatings still deliver superior corrosion protection performance. Different alternatives (aluminum coatings, zinc nickel coatings, etc.) have been suggested over recent years for different applications, but none of these provide all the properties that made cadmium such an important coating.

Despite environmental pressure, cadmium is still widely used in industrial application such as fasteners, electrical connectors and aerospace components. In particular for aerospace components, long lasting corrosion protection on complex geometry components is required.

The throwing power of cadmium plating baths is limited and recessed areas are difficult to reach. Attempts to address low deposit areas often rely on the operator skills. Reproducibility and full traceability are not possible for such operator dependent processes. Quality control and thickness specifications are hard to validate as layer thickness values in most recessed areas are difficult if not impossible to measure by non-destructive means.

Engineering solutions for cadmium plating applications

Cadmium coatings have excellent properties for which an adequate substitute has not yet been found. Different alternatives for different applications have been suggested over recent years (aluminium coatings, zinc nickel coatings, etc.) but none of these holds all the properties that made cadmium such an important coating.

Despite environmental pressure, cadmium continues to be widely used is industrial application such as fasteners, electrical connectors or aerospace components.

In particular for aerospace components, long lasting corrosion protection on complex geometry components is required. Achieving the minimum layer thickness is often impossible when using only the main tank anodes. In practice, brush plating patch-ups or other manual plating operations seem to be common.

Manual operations are problematic because not only they are entirely operator dependent and thus very irreproducible, but also because there is no traceability.

Understanding that a component should be plated consistently throughout different shifts, Elsyca's Advanced Engineering Services (AES) team aims for user-friendly solutions where the operator's responsibility is limited to loading and unloading the part and launching the rectifier program.

The current distribution is ensured by the tooling configuration itself, resulting in a reliable, reproducible, traceable and operator independent result.

Tooling solutions typically consist in a collection of current robbers, insulating shields and auxiliary or conforming anodes. If conforming anodes are fed by multiple rectifiers, this will additional control of the current density distribution over the part. When required, Computed Aided Engineering (CAE) work is extended to fluid flow simulations, in order to ensure minimum electrolyte refreshment around the part and elimination of gas pockets. Tooling and support fixtures design account for practical limitations with respect to manufacturability, hardware cost and maintenance issues.

Elsyca has range of AES available for cadmium plating, starting with the electrolyte characterization, where the electrochemical properties of a cadmium bath are collected.

A process diagnostic can be quickly achieved with a Plating Feasibility Analysis where the plating process performance can be simulated for the existing or foreseen plating tank and tooling configuration. These valuable data can be used internally for further process improvement or for marketing purposes, in order to demonstrate the plating performance to an end-customer.

Elsyca has a vast experience in Computer Aided Engineering (CAE) projects that encompass the development of cadmium plating tooling for complex components, thereby delivering a complete plug-and-plate solution. Once the tooling is mounted around the component and the rectifier program started, the tooling solution will deliver the correct amount of current to each surface area of the part. This guaranties not only a plating performance that by far outperforms state-of-art cadmium plating operations, but also rules out the lack of reliability as caused by manual interventions. An example of the plating performance that can be obtained from an Elsyca developed tooling configuration for a landing gear part can be found here.

In the context of a Computer Aided Engineering (CAE) project, Elsyca's Advanced Engineering team will develop an optimal tooling solution by iterative simulations using Elsyca's PlatingMaster software package. Starting from the component and infrastructure geometries and respecting all practical limitations, a complete tooling solution is designed. Such tooling is designed to deliver an optimal current density distribution, avoiding excessive local current densities and deposits out of specification. The deliverables of a CAE project include the 3D CAD files of the tooling assembly and the complete bill of materials. Optionally 2D technical drawings can also be generated.

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