Page 43 - CFCM Nov-Dec-2020 Final_Neat

pending on the chemistry of the plat-
ing solution) need careful operator
protection (PPE and OSH requirement)
and environmental protection such that
there is no loss of solution to the en-
vironment. The process is messy and Figure 4: Preparation of the static port for anodizing. a) masking painted circle,
prone to spills and plating chemicals b) Scotchbrite cleaning, c) masking with catchment, d) anodizing.
tend to drip onto the floor and run
down the object being plated. When the process is carried of the static port, the anodizing process took
out on aircraft, great care has to be taken to prevent plating 30 minutes to achieve ~7 m coating thickness,
chemicals from running into the aircraft itself. This usually which is close to the maximum time that a maintainer
necessitates extensive masking to keep the plating chemicals could continuously move the tool overhead.
contained and creating runoff channels to catch them. Plat- The temperature of the anodizing solution was
ing overhead is particularly difficult because chemicals can 28 deg. C (82 deg. F)
easily drip onto the operator. When the plating chemicals 7. DI rinse using a single-pass system with the
are toxic (e.g. cadmium, chromium plating), highly regu- Dalistick tool
lated (e.g. chromates), or corrosive (e.g. sulphuric acid) 8. TCP seal using the closed-loop tool
brush plating may pose a significant environmental and/or 9. DI final rinse with the Dalistick tool
OHS concern. 10. Warm air dry
In order to overcome these concerns, the French com- 11 QA – electrical insulation measure by multimeter,
pany Dalic developed the Dalistick non-drip selective area thickness measured by dry film gauge
plating and anodizing equipment that can be used in any
orientation. Because the process is non-drip, the only items of per-
The principle of the Dalistick is shown in Figure 2. The sonal protective equipment needed, even when plating
electrolyte is held in a reservoir or bottle, from which it is overhead, are vinyl gloves, safety glasses and lab coat.
drawn by a peristaltic pump (blue circuit) and fed into the There is no need for the rubber aprons and thick rubber
plating tool. The tool is constructed so that the electrolyte gloves typically used by brush platers.
runs into the center of a pad, while air and electrolyte are
both drawn out around the periphery by a second peristaltic COnCLuSIOn
pump (red circuit) that has a higher pumping rate. The Brush or selective plating has made incredible strides since
flow rates of electrolyte delivery and electrolyte plus air re- its development in the 1930s and subsequent improvements
turn are balanced so that the pad is properly wetted, but in the 1950s and 60s.
excess electrolyte does not build up and drip out of the Brush plating is used in several industrial sectors for in-
pad. This ensures that the surface being plated or anodized situ repairs where tank plating is not possible because of
remains wet to allow a constant ionic path, but the tool the size of the part.
does not drip, regardless of its orientation, and regardless The Dalistick developed by Dalic in France now allows
of whether it is being used on the surface or held in the non-drip selective plating and sulphuric acid anodizing
air, obviating any need for a seal around the plating area. with minimal operator and environmental issues. This tech-
Figure 3 shows the Dalistick being used to repair the nology can probably be considered state-of-the-art.
Static Port on the P-8. The process is finding increasing application in aerospace
The process for this specific repair is: (Figure 4) plating, where LHE zinc-nickel is now replacing the use of
1. Clean the static port area to remove gross toxic cadmium. n
contamination
2. Mask the peripheral paint circle and the central Peter J Paine is Principal, P. J. Paine & Associates.
sensor holes He can be reached at pjpinc@rogers.com or (613) 884-9029.

3 Clean and prep the entire area within the red painted
References
circle with fine Scotchbrite Non-Drip Selective Plating and Anodizing for Aircraft
4. Attach a catch basin with aluminum tape to catch the Dr. Alan Rose, Corrdesa LLC (arose@corrdesa.com; 7706833960),
Dr. Siva Palani, Corrdesa LLC , Dr. Keith Legg, Corrdesa LLC,
runoff – a thin liquid layer on a vertical surface coa- Vivien Kibble, Corrdesa LLC
lesces and runs off. A larger tool would eliminate the
runoff by sucking the liquid away before it coalesced Acknowledgements
The writer would like to thank Dr. Alan Rose, CEO Corrdesa LLC.,
5. Clean the area with acetone Dr. Keith Legg, CTO Corrdesa LLC. and Corrdesa LLC.
6. Anodize using the closed-loop system – because of They may be reached at Corrdesa.com
the small size of the standard tool and the large size

www.cfcm.ca CAnADIAn FInISHInG & COATInGS MAnuFACTuRInG 43