The application potential and benefits of selective, brush plating for aerospace applications. By Derek Vanek
Why take the surface to the tank when you can take the tank to the surface? This is the idea on which the portable, selective, brush plating process is based. Applying engineered surface coatings can provide a wealth of benefits, including protection against corrosion and wear. However, with many surface finishing options available, including thermal spray processes, IVD, PVD, tank plating and selective, brush plating, choosing the right one for a particular application can be a complex task. So, when should you choose selective, brush plating? Here, we discuss the application benefits and possibilities of selective plating for the aerospace industry.
There are many benefits to choosing selective plating, including accurately focusing the plating onto specific areas of a component, enabling the parts to be plated in-situ and helping to minimise downtime and production delays.
Selective plating is best suited for localised areas on simple shapes such as inside and outside diameters or flat surfaces. In contrast to tank plating, the Sifco process does not require extensive masking or special fixtures to plate the component. The length of time a plating operation will take is primarily determined by the amount of material that needs to be applied. With the Sifco process, deposits can be plated at rates that are 30 to 60 times faster than conventional tank plating.
The performance and cost differences that these factors make to maintaining, enhancing or repairing critical components can be significant, which is why it is important to consider all of the variables involved before deciding which surface finishing process to specify.
Although damage from wear, corrosion or mis-machining can be repaired using selective, brush plating, this process should not only be considered for repair or salvage. The range of pure metal and alloy deposits available with the process offer enhanced wear resistance, increased surface hardness, low electrical contact resistance and/or corrosion protection for OEM component applications.
Aerospace is an industry that is highly demanding when it comes to surface finishing performance requirements and the aerospace industry is renowned for its robust standards for the manufacture and repair of its high performance equipment. Components need to be able to withstand friction, extreme temperatures and corrosive environments while continuing to operate at optimum levels.
The aerospace industry was one of the first to widely accept and approve selective plating to restore worn and corroded metal components. A good example is the Federal Aviation Administration’s Advisory Circular 43.13-1B, which contains methods, techniques and practices (including selective plating) acceptable for the inspection and repair of non-pressurised areas of a civil aircraft when there are no manufacturer repair or maintenance instructions.
Selective plating is also approved worldwide by most major airlines, landing gear and engine manufacturers, and is specified in overhaul manuals and standard practices. Recently, Sifco ASC was listed as a Boeing Approved Supplier for selective plating services. This was achieved after demonstrating the process controls and manufacturing capability for plating following a comprehensive technical review from Boeing. It therefore allows Sifco ASC to provide its cadmium brush plating services to BAC5854 and BAC5849. The company’s association with Boeing also includes approvals for mechanical and chemical testing. Sifco ASC works closely with customers in the aerospace industry to offer practical, cost-effective options for repairing and enhancing the surfaces of components. One example is the travel kit it provided for touch-up applications, specifically designed for the aerospace industry and ideal for aircraft on ground (AOG) operations where time is critical.
A typical operation
The Sifco process was developed more than 50 years ago. It was initially used for industrial repair applications with early acceptance by the US Navy. Over the years, it was developed to service a wide range of industrial repair and manufacturing applications.
The range of metals used in selective plating is extensive. The Sifco process is used to apply any metals that are traditionally carried out by tank electroplating, the most common being; nickel, copper, cobalt, nickel-tungsten, cobalt chromium carbide, silver, gold and platinum.
There are several preparatory steps in which a work area is prepared to receive an adherent deposit. The appropriate preparatory procedure is determined by both the substrate of the component and the plating solution to be applied.
The process can be carried out manually, it can be mechanised or it can be automated for high-volume applications. The thickness of the plating is accurately controlled through use of an ampere-hour meter and once the required ampere hours are reached, plating is stopped and finished with a final water rinse then dried.
Automating the process for high volume
Selective plating is a precise and effective method for the enhancement of localised surfaces on OEM components and can be mechanised or fully automated to meet the demands of high volume plating applications.
Sifco ASC recently developed a semi-automated workstation for Powell Electrical Systems, a division of Delta/Unibus, which reduced the processing time to selectively plate non-cyanide silver onto each side of its copper bus bars by 90%.
Its portability and versatility has allowed the Sifco process to be employed in some of most challenging locations and applications around the world including submarines, space stations, hydro-electric power stations, nuclear power plants, oil rigs in remote locations and on critical aircraft components.
Selective, brush plating has dramatically evolved from its origins of touching up existing plating jobs, and is now considered an overarching term describing a highly technical process used for repairing or improving the surface properties in an array of circumstances. It is specified in the initial engineering design specification as well as being called out for component repair.
Derek Vanek is with Sifco ASC.
Inside diameter repair applying AeroNikl® on a component for wear resistance.jpg
SIFCO ASC Touch up kit.png
Outside diameter repair applying Nickel on a component for dimensional restoration.jpg
On-site repair on an outside diameter of an industrial component.jpg
On-site repair on an outside diameter of an industrial component v2.jpg