BY ALAN M. PETRILLO
Protecting a fire apparatus from corrosion like what occurs from road salts, salt water air, and chemicals can take on a number of forms, from coatings to immersion processes and corrosion-resistant materials.
Fire Apparatus & Emergency Equipment talked with a number of apparatus manufacturers about the various types of corrosion protection they use on their fire apparatus chassis and bodies.
Dave Reichman, national sales manager for Rosenbauer, says that Rosenbauer chassis have been hot dip galvanized for quite a few years. “The majority of our chassis are hot dipped—the frame rails, extension pieces, and front bumper extension—using a molten zinc preparation,” Reichman notes. “It’s the same process as what is used for roadway signposts and guard rails. We hot dip each frame rail, drop members, and extension pieces before assembly, so there are no missed spots.”
Reichman points out that on aerial devices, Rosenbauer also hot dip galvanizes the torque box, outrigger system, and jacks after the torque box is welded together. “Ladder sections can be hot dipped galvanized if the fire department wants it,” he observes. “We have a patent on the process where the molten zinc is flowed inside the tubes of the ladder to give protection both inside and out. We also make a CRT body, which uses corrosion-resistant technology in its design. It’s 12-gauge stainless steel bolted and can remain as brushed stainless or be painted if the customer wishes.”
Doug Kelley, engineering director for KME, says KME offers two options for corrosion protection on chassis. “One option is to galvanize the frame rails with a hot dip zinc coating,” Kelley says. “The other is a Tectyl coating between the frame rails, which is the hardest place to protect because moisture can get trapped in there and it’s difficult to get it out. So, we make a sandwich with this coating in the middle between the two frame rails.”
1 These frame rails in the KME shop have been hot dip zinc galvanized to protect against corrosion. (Photos 1-2 courtesy of KME.)
2 KME has applied a Tectyl coating between these two frame rails to prevent moisture from getting trapped between them.
Kelley notes as a base for every truck it builds, KME makes sure it applies paint according to the specific manufacturer’s specifications to get the best resulting finish. He adds that, in some areas of the country, fire departments are having either Line-X or Rhino seal coating applied to the chassis to protect it from salts and corrosive chemicals used on winter roadways.
KME also uses dielectric barriers on all its fasteners, Kelley says, which are designed to prevent water entry. “All the screws, bolts, nuts, and washers have the coating put on them when we buy them,” he says. “These dielectric barriers can also take the form of gaskets, tape, or coatings that are sprayed or brushed on.”
Drew Sutphen, president of Sutphen Corp., says Sutphen starts with the frame rails because they are the key to corrosion. “We blast and strip the paint applied by the frame rail manufacturer to original white metal,” Sutphen says, “then put on two coats of a green inorganic zinc-rich coating that etches into the raw steel. This is a product that’s been used in the marine industry and cell towers with great success. After those two coats, we top coat with Imron paint (now Exalta) in a seven-step process. Four years ago, we implemented this process on every steel bracket, turntable, jack tube, side plate, and everything else on our aerials.”
3 Sutphen applies a yellow zinc dichromate coating, then a clear coat on its Grade 8 bolts used as structural fasteners. (Photos 3-4 courtesy of Sutphen Corp.)
4 The arrow shows the barrier tape that Sutphen uses to prevent two dissimilar metals from touching.
With a raw aluminum cab and body, Sutphen says his crews wash and degrease the metal with solvent to remove any contamination, then sand it with 400-grit or finer sandpaper to open up the aluminum. “Then we wipe it down again, apply a self-etching primer, then put on a Cathacoat polyurethane base coat, followed by an Imron polyurethane top coat,” he points out. “The finish is very corrosion-resistant, and the key ingredient is the zinc-rich self-etching primer that bites into the aluminum and seals it, retarding corrosion.”
Sutphen says his workers predrill every bolt and bracket hole before painting so that the paint can get into the holes and behind the brackets. “All our stainless steel fasteners are treated with a yellow nylon coating on their threads, and if we have to drill into metal and can’t use a nylon-coated screw, we use Eck, a zinc-rich spray or paste, on the screw before we insert it,” Sutphen notes.
Joe Hedges, product manager for chassis and aerials, says E-ONE’s single and double frame rails are hot dip galvanized in zinc, then powder coated. “Where aggressive deicing agents are applied, all the chassis cross members, battery boxes, and most bolts are hot dip galvanized as well,” Hedges observes. “E-ONE has its own salt dip spray chamber on site where we test various products to determine how well they hold up. After testing chassis hardware, we changed the nuts, bolts, and washers that the chassis is assembled with to hardware coated with Geomet 720, which is a dull gray coating that does an amazing job protecting against corrosion.”
5 E-ONE ‘s frame rails are hot dip zinc galvanized coated and then powder coated to protect against corrosion. (Photos 5-6 courtesy of E-ONE.)
6 E-ONE uses stainless steel fuel tank straps on its aluminized steel fuel tanks.
Hedges says E-ONE has been using stainless steel fuel tank straps for years to hold its aluminized steel fuel tanks, and that E-ONE also offers the option of stainless steel fuel tanks. “We also offer stainless steel air tank straps as an option to hold the corrosion-resistant air tanks we use, which are powder-coated externally and internally by our supplier.”
A year ago, E-ONE changed all of its CAN network cables in the chassis and body to special sealed cables to prevent water intrusion and to Deutsch connectors that improve sealing by keeping the seal intact, Hedges says. “We also use Eck sealant on threaded fasteners and prepunch holes in body panels so the holes are painted. On the electrical connections outside the chassis that are exposed to weather, we spray them with NanoProtech, a thin clear spray that works very well.”
FERRARA FIRE APPARATUS
Ronny Allen, marketing director for Ferrara Fire Apparatus, points out that all of Ferrara’s frame rails are powder coated, and it offers F-Shield, a Line-X product applied to the frame rails, cross members, fuel tank, and air reservoirs, as well as body parts and compartments, if the department desires it. “After the frame rails are put together and coated, we then seal the gaps between the rails for added protection,” he says.
“The interiors of our cabs also are painted with F-Shield to prevent corrosion and to deaden sound,” Allen notes. “We first spray on a precoat so there is no exposed aluminum, and then apply the F-Shield material. We’ll do it on bodies, bumpers, grilles, fenderettes, and tire rims too, and it’s offered in black and gray colors.”
Bill Doebler, vice president of sales for HME Ahrens-Fox, says, “We are a full-fledged stainless steel manufacturer, so all of our pump bodies and piping don’t require coating, but some departments want various areas to be painted. We were one of the earlier pioneers in galvanizing the chassis frames, and because road treatments are so harsh, we galvanize cross members, fasteners, and support structures too with a hot dip zinc composite.”
7 This HME Ahrens-Fox chassis has been hot dip zinc galvanized. (Photos 7-8 courtesy of HME Ahrens-Fox.)
8 The front bumper of this HME Ahrens-Fox pumper has been coated with Line-X.
Doebler notes that HME Ahrens-Fox has seen a shift toward using Line-X and Rhino coatings on many areas underneath fire apparatus, as well as in areas that take a beating. “Departments are moving away from polished chrome front bumpers to structural steel bumpers painted and coated with Line-X for abrasion resistance and as a corrosion protectant,” he says.
“Everywhere on a vehicle where there are dissimilar metals we have a barrier between them,” Doebler says. “For example, on a handrail made out of cast material placed on stainless steel, where the screw goes through, we have special gaskets that mushroom out around the screw head so there’s no opportunity for moisture to intrude or come in contact with the other metal. Where fenderettes are attached to custom cabs and bodies, we put a 1¼-inch gasket in between to prevent material from getting trapped.”
4 GUYS FIRE TRUCKS
Mark Brenneman, assistant sales manager for 4 Guys Fire Trucks, says, “We build our bodies and subframes out of stainless steel exclusively, so when you start with a material that doesn’t corrode, you don’t need to do much more.” However, he adds, “When aluminum and steel touch each other, we use a double-faced molding tape where they meet.”
Jay Vogltance, plant manager for Danko, says his company first does an acid wash on all aluminum or steel parts of a body to decontaminate them and make paint adhere, then applies a two-part epoxy primer, followed by a two-part top coat, and then a clear coat. On a chassis, “We do a hybrid undercoating that seals the surface so it’s resistant to salt and other chemicals,” Vogltance notes. “We use a corrosion-resistant sealing on all the equipment, screws, bolts, and anything that will have metal on metal contact. We use a dialectic grease that seals moisture out and prevents corrosive reactions.”
9 A technician applies a two-part epoxy primer to this Danko apparatus body, which will be followed by a two-part epoxy top coat and a clear coat. (Photos 9-10 courtesy of Danko.)
10 Danko applies Line-X coating inside compartments when customers request it.
Mark Kreikemeier, Danko’s president, says Danko has been using hot dip galvanizing since the late 1970s on its tankers that use a steel substructure and tank cradle. “They’re coated with a hot dip zinc material that we have done at a facility nearby,” he says. “And, we also install diodes on the intake and discharge side of the pump in order to eliminate electrolysis problems.”
Wayde Kirvida, sales engineer for CustomFIRE, points out that his company has had the most success battling corrosion when customers select stainless steel for construction instead of aluminum. “With a stainless steel subframe, we use a 3M electrolytic barrier between the body and the subframe,” Kirvida says. “We use a Sutphen chassis, which has a cathode chemical treatment,” he says, “and we also use Spartan chassis that have galvanized frame rails and components.”
Kirvida says CustomFIRE offers stainless steel fuel tanks and tank straps, battery boxes, front bumpers, water tank frames, and underbody supports. “We use plastic fastener sheaths so the metal on the fastener never touches the metal on the body,” he says, “silicone caulk around brackets in the frame rails, and put all wiring inside the body and not outside except for underbody lights.”
Todd Nix, apparatus consultant for Unruh Fire, notes that Unruh uses the same undercoating on its apparatus as the U.S. military does, Z-Guard 2500. “We apply it as standard and also spray it on the bodies before we mount them as well as on bolts, nuts, and screws,” Nix says. “Any penetration in the chassis or body is siliconed to be waterproof and protected from corrosion. We also add a ¾-inch rubber separator between the frame rail and the body to protect against galvanic dissolution and allow the body to flex.”
11 Unruh Fire applied Line-X on this apparatus body at the request of a customer. (Photos 11-12 courtesy of Unruh Fire.)
12 Unruh adds a ¾-inch rubber separator between the frame rail and the body to protect against galvanic dissolution and to allow the body to flex.
13 Technicians at SVI Trucks apply a PPG Delfleet Evolution coating to an apparatus body. (Photos 13-14 courtesy of SVI Trucks.)
14 SVI Trucks isolates the steel chassis frame from aluminum bodies and subframes using 3⁄8-inch-thick UHMW plastic extrusions.
15 Midwest Fire builds fire apparatus with polypropylene bodies, which are impervious to corrosion. (Photo 15 courtesy of Midwest Fire.)
Chris Woelhof, paint manager for SVI Trucks, says that SVI uses PPG Delfleet® Evolution fleet coating system. “For our underbodies, we coat with Auto Armor Sound Shield, a black spray-on rubber coating,” he says. “Our aluminum bodies and subframes are isolated from the steel chassis frame using 3⁄8-inch-thick UHMW plastic extrusions, and we also use plastic isolators on all stainless steel fasteners going into aluminum bodies. “SVI also uses Eck for corrosion protection around door handles, roll-up doors, compartment hinges, and where dissimilar metal corrosion can occur.”
Jeff Bowen, account representative for Midwest Fire, says that by using an all polypropylene body, “there’s not a lot we have to do for it regarding corrosion protection. Lots of departments like polypropylene bodies because they are impervious to rust.”
ALAN M. PETRILLO is a Tucson, Arizona-based journalist, the author of three novels and five nonfiction books, and a member of the Fire Apparatus & Emergency Equipment Editorial Advisory Board. He served 22 years with the Verdoy (NY) Fire Department, including in the position of chief.