The Bare Facts of Bare Metal

Whether working on classics or the latest jets, eventually you’ll face polished aluminum. The more you know, the better the finish.

To say that polishing aluminum is one of the least popular projects for a technician is an understatement. Do it right and you’ll beam almost as bright as the aircraft’s shine. But do it wrong and you’ll spend hours rubbing and buffing to complete frustration.

Few technicians receive any formal training in aluminum polishing. So with the help of people who do this every day, we’ve gathered guidelines to keep you from polishing yourself into a corner.

Technicians generally will be asked to restore old or damaged surfaces, like those on a classic or antique, or polish the bright work on a new business jet’s leading edges or intake rings. The tasks are similar, but not the same.

Restoring weather-beaten aluminum to a factory-new finish is a long, tedious process. Polish is the only protection bare metal has against salt, sun, and moisture. Left unprotected, it is quickly marred by surface corrosion.

"The time and effort needed to restore bare aluminum is purely dependent on the condition of the metal right now," explained Tom Numelin, president of PerfectPolish. If it’s in good condition, you can get a passable finish on a small airplane in about 40 hours. Abused or scratched metal "can take all the time you have to give."

There are two approaches to restoring old aluminum, Numelin said. The first is "cutting" using rouge bars and special wax. It’s quite effective, "but it requires considerable expertise," he said, as well as specialized equipment. "Workers must wear protective clothing, because the rouge ends up coating everything." Cutting is usually limited to a shop specializing in restoration.

The most common method is compounding, Numelin said. It uses the same equipment as car compounding–a right-angle orbital buffer and wool pads. For most applications, he said, you could use a quality rubbing compound like those from 3M or one of PerfectPolish’s more aggressive Nuvite polishes, which range from heavy cutting to fine finish.

"Compounding requires a minimum amount of specialized equipment and only trial-and-error expertise," he said. "That’s why it’s the method most used by maintenance shops. Properly done, compounding can remove light scratches and surface corrosion and leave a surface that’s bright and smooth to the touch."

To maintain the finish, Numelin recommends the use of Silane’s Glass Wax or something similar. He warned against using anything with ammonia, which will etch the aluminum.

Before you polish an entire airplane, he said, make sure it will be parked in a hangar. "Rain and sun will turn a finely polished finish into a streaked and spotty mess in just a couple of months," he added. Finishes of aircraft kept outdoors must be maintained continually. So if it’s going to sit outside, paint it.

Most maintenance shops will never get asked to polish an entire airframe, but there is a good chance you will need to polish leading edges and inlets on a business jet. This is not just for looks, said Ricky Waldrup, owner of Great Lakes Aircraft Detailing. "The high temperatures achieved by heated leading edges can promote corrosion. So while metal polishing may seem purely cosmetic, it is really a valuable part of preventative maintenance."

A properly done finish should make the aluminum look like chrome, he added. "No doubt, it’s a lot of work but when it’s done right there’s a lot of pride to it. The shinier you get the finish, the longer it lasts."

One of the major mistakes technicians make is using the wrong type of polisher. An automotive-style orbital buffer is a bad choice, Waldrup said. It is slow and hard to operate, and can build up damaging excess heat. "You can get into a situation called ‘clad shearing’ where you remove the cladding finish. Once that’s done, there’s no way to bring it back."

If you’re going to do any amount of metal polishing on business jets, he said, invest in a quality pneumatic drum polisher. It avoids overheating the metal and makes the job go a lot faster. "With the right tools, you can do the bright work on a Falcon 2000 in about eight man-hours," he added. An orbital polisher takes at least twice that.

"Trying to take shortcuts will just end up costing you a lot more time and create a lot more frustration," he said.

A good drum-polishing setup costs $2,000 to $3,000, Waldrup said. "But by the time you’ve polished your second Gulfstream III or IV, it has paid for itself in pure man-hour savings alone."

He also said you should pick the right polish. He recommends a buffered polish that will start out coarse and get smoother as you use it, producing a shiny finish. Be careful with automotive rubbing compounds, he said. Many have a lot of silica in them, which can leave a gray cast to the metal. "It’s hard to get it out."

It is important to keep up with the finish. That includes proper cleaning after each flight. "Always wipe down the metal with an appropriate solvent to remove dirt and bugs," Waldrup said. Don’t clean it and you’ll get oxidation that can lead to pitting. "No matter how shiny it is, that’s still bare metal out there in the weather," he said. "You need to keep the dirt, carbon, and whatever else the jet flies through off the surface."

Waldrup suggests you re-polish the bright work about every three months. "With the proper tools, it’s beneficial to the metal to polish it frequently," he said. "Besides, it keeps it looking sharp and that makes the CEO happy."

Contact

Great Lakes Aircraft Detailing (Rick’s Aircraft Paint and Polishing)
Pontiac, Michigan
Phone/Fax: 248-969-8316
www.airplanepolishing.com

Tentex Company/PerfectPolish
Phone: 877-370-0269 or 707-283-2014
Fax: 707-775-2843
www.perfectpolish.com

3M (rubbing compound)
St. Paul, Minnesota
Phone: 888-364-3577 or 651-737-6501
Fax: 800-713-6329 or 651-737-7117
www.mmm.com

Advanced Silane Technology (Glass Wax, MicroBrite protector)
Palm Coast, Florida
Phone: 800-549-2539
Fax: 386-445-0471
www.adsil.com

Flitz International (metal polish)
Waterford, Wisconsin
Phone: 262-534-5898
Fax: 262-534-2991
www.flitz.com

Met-All Industries (metal polish)
Canal Fulton, Ohio
Phone: 330-854-1122
Fax: 330-854-1133
www.met-all.com

Nuvite Chemical Compounds (metal polish)
Brooklyn, New York
Phone: 800-394-8351
Fax: 718-383-0008
www.nuvitechemical.com

Transport Buff (polishers, Miracle Finish compounds)
Fremont, Ohio
Phone: 419-332-5110
Fax: 419-332-5158
www.transportbuff.com