Plating on titanium is increasing in popularity thanks to the metal’s unique properties, but the process comes with many challenges. Derek Kilgore, engineering manager at SIFCO ASC, discusses how automation and selective electroplating can overcome these hurdles safely, efficiently and cost effectivey.

Titanium is an abundant and remarkable material widely used in industry. Though lightweight, it has an exceptionally high strength-to-density ratio. It also has a high melting point, low thermal expansion and outstanding resistance to corrosion, all of which make it the material of choice for many demanding applications, ranging from automotive, marine and sports equipment to mission-critical applications in aerospace and healthcare.

However, due to tribological properties – including a high friction coefficient and poor abrasive and adhesive wear resistance – titanium alloys have limited use for essential components (e.g., aircraft landing gears and automotive internal combustion engines) unless they are plated effectively. Doing so can enhance the metal’s properties, including surface fatigue, anti-galling and fretting behavior. Plating can also introduce other key performance characteristics, such as improved lubricity, corrosion resistance and conductivity, as well as heat reflection and emissivity. Plating also improves the metal for brazing and can be used to resize, repair or salvage titanium components.

Unfortunately, titanium is notoriously difficult to plate, largely because of an oxide film that forms the moment it becomes exposed to oxygen. Acting as a protective layer, this is hugely beneficial in terms of titanium’s industrial performance. It also acts as a literal barrier to plating, however, limiting the strength and efficiency of bonds. Hydrofluoric acid can be used to remove this oxide prior to plating, but it is both a contact poison and highly corrosive. As such, it introduces significant health and safety risks. Furthermore, typical activities during tank plating – including surface roughening by abrasion, grit blasting and etching – can also encourage the oxide to reappear. In a worst-case scenario, this leads to scrappage and waste of a high-value material.


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Photo1: Titanium selective electroplating on an impeller (before)

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Photo 2: Titanium selective electroplating on an impeller (after)


A Safer, More Efficient Plating Process

In its quest for a fluoride-free electrolyte and a safer and more efficient plating process, SIFCO ASC undertook extensive experiments with TI 6-Al 4-V and TI 6-6-2, two of the world’s most widely used titanium alloys. The result is a plating process that includes surface pre-treatments of mechanical finishing followed by an etch, activation and finally the introduction of a thin layer of nickel. This pioneering approach brings all the benefits of selective plating, including versatility and convenience, together with enhanced safety and component quality.

Just like selective electroplating with other metals, this process can be delivered manually. However, there are complications. To avoid oxidization, the electrolyte solution must flow continuously over the component at all times. If any aspect of this sequence is compromised, the likely result is oxidization and scrappage, leading to waste. This means that, manually, the process is challenging, time-consuming and must be undertaken with extreme care. These problems, however, can be virtually eliminated through automation.


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Photo 3: A flow anode is ready to plate a titanium cylinder.)

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Photo 4: A flow anode plates nickel in a titanium cylinder in a lathe on SIFCO ASC’s titanium plating cart.


Automation is Key to Productivity and Safety

The benefits of automation are being felt across manufacturing. Selective plating onto titanium is a process that lends itself perfectly to this approach, reducing the possibility of human error while also bringing many advantages.

By ensuring more-reliable plating, automation improves product quality and reduces the need for machining and post-plating work. It also works around the clock. Throughput and productivity are there-fore enhanced.

With etching undertaken in a closed-loop system, SIFCO ASC’s automated process also eliminates the need for hydrofluoric acid, bringing an immediate health and safety benefit. Importantly, because the entire process is fully automated, operators are no longer in regular or direct contact with plating solutions. The only requirement is to replace or dispose of solutions, greatly reducing their exposure and risk. Equally, by replacing repetitive and ergonomically inefficient manual tasks with automation, employee satisfaction and well-being are also improved.


Repeatability and Traceability

Because of its superior properties and performance, titanium is most often deployed in mission-critical applications where absolute and consistent quality is demanded. Each component must meet the same demanding specifications with full traceability.

Here, automated systems deliver an obvious benefit. For each application, accurate settings and data logs can be stored so that parts are plated in the same way, even if there’s a time lapse between lots. Deviation from settings is therefore virtually eliminated. Apart from ensuring a consistent and repeatable process, it is also fully traceable, which makes it easy to identify specific components should there ever be the need to investigate or recall specific products.


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Photo 5: SIFCO ASC’s custom titanium plating cart incorporates automated solution flow systems and data logging.


A Bespoke Solution

Calling on its selective-plating expertise and experience, SIFCO ASC has developed a bespoke range of automated solutions to meet customer needs.  At one end, there are portable and programmable power packs that allow repairs or plating to be undertaken in situ. Instead of manually changing the plating parameters like in manual systems, the operator simply programs the time, amperage and thickness of deposit. This eliminates human error and minimizes the risk of oxidization for titanium applications.

Alternatively, SIFCO ASC can design, specify, deliver and commission simple workbenches or fully automated workstations with robotic systems to handle components, anodes and solutions through RFID and barcode tagging. The only human intervention necessary is programming and replenishing solutions. In this respect, as selective plating deposits onto a very localized area, there’s no need to use harmful chemicals on the titanium surface due to the reduced risk of an oxidized layer forming, which brings associated cost, health and safety benefits.

For manufacturers with their own in-house facilities, automated selective plating offers a more flexible and cost-effective solution than conventional tank plating. This includes reducing the floor space required with tanks, which immediately gives businesses either more room to undertake other activities or cuts down on the costs associated with renting and running these spaces.

For those that rely on sending components away for treatment, significant benefits include faster turn-around and reduced downtime, along with lower transport costs and carbon footprint. These sustainability factors are further enhanced by minimizing the use of toxic chemicals in the process.

SIFCO ASC has worked with manufacturers globally to undertake evaluations of current processes and present detailed and fully costed bespoke recommendations. Training and support have also been provided throughout implementation and beyond to ensure the solution meets expectations.


Conclusion

Titanium offers almost unlimited potential to drive improvements in the reliability and performance of mission-critical components such as combustion engines and aircraft landing gears. While this benefit is within reach, it has also proved challenging to grasp – largely because of the complications surrounding the all-important plating process.

These challenges can be essentially removed through investment in SIFCO ASC’s automated systems. Combining the ease and convenience of selective plating, they not only reduce human error but also introduce vital benefits in terms of quality, repeatability and traceability, as well as productivity and user safety.


All images provided by the author.