Taking Plating Technology to the Aircraft

Brush plated cadmium, zinc-nickel, tin-zinc, nickel, tin, and zinc deposits on steel have been salt spray tested per ASTMB-117. The brush plated deposits meet or exceed the requirements for tank electroplates when compared to AMS and military specification requirements.

Brush anodized coatings have been tested and meet the performance requirements of MIL-A-8625E, AMS 2470, AMS 2468, AMS 2469, and BAC 5623.

Hydrogen embrittlement:

Cadmium, zinc-nickel, and tin-zinc plating solutions have been specifically developed for plating or touching up high-strength steel parts without needing a post-plate bake.

The most common deposits used when brush plating aircraft components are cadmium, zinc-nickel, and tin-zinc. These deposits are brush plated onto localized areas of landing gear to repair damage caused by runway debris or other mechanical damage. Additionally, a common application is plating sulfamate nickel to localized areas of engine components to improve the brazing process.

The brush plated cadmium, zinc-nickel, and tin-zinc are low hydrogen embrittling deposits, and can be applied to localized areas for touchup of defective tank plated cadmium deposits without a post-plating bake. They can be applied to the component in-situ, on the plane with minimal to no masking. It is a fast and simple repair — solvent clean, mechanically abrade, and plate.

Brush plating: Repairing damaged cadmium plating on a landing gear

During a routine maintenance inspection, the operator discovered several damaged areas on the landing gear, including two bushing diameters. There were several small areas of damage that penetrated both the paint and the underlying cadmium plating. This localized damage was a good candidate for repair by brush cadmium plating because it could be done without any disassembly of the landing gear.

Carrying out the repair

The individual defect areas to be plated were solvent cleaned first. They were then mechanically abraded with 120 grit aluminum oxide sandpaper to slightly feather the defect area and to clean the area to be plated.

Because the surface was painted, the only masking that was required was used to catch the small amount of runoff of the plating solution.

The absorbent plating tool was placed into a small container of the cadmium plating solution to soak for a few minutes prior to plating. The positive lead was plugged into the anode, and electrical contact from the power pack was made by attaching the negative lead to a conductive area near the damage.

With the power pack voltage properly set, the deposit was applied by rubbing the saturated anode on the defect area in a circular motion until the calculated ampere-hours (to achieve the desired thickness) were passed. The area was water rinsed and dried.

Bushing repair

The bushing repair was carried out in a similar fashion, with minimal masking to control the solution. The surfaces were solvent cleaned, mechanically abraded, and the cadmium was applied to the bores and faces of the bushings.

Once the plating was completed, the chromate conversion coating was applied to the plated areas for 30 seconds. The areas were rinsed and air dried.

At this point, the repaired areas on the landing gear were ready for the touchup paint to be applied. The plated bushings were ready for service.

Summary

Selective plating is a widely used tool in the aerospace industry for both repair and OEM applications, offering portability, flexibility, and high quality coatings. It can help minimize aircraft downtime and return aircraft to full functionality.

Derek Vanek is the manager of inside sales and technical support at SIFCO Applied Surface Concepts. He has been with the company since 1981, and holds a BS in Business Administration from Old Dominion University. For more information visit www.sifcoasc.com.