Bust the rust

By Paul Abelson
senior technical editor


What’s the best way to remove corrosive salts from those hard-to-reach places on your truck? If you said with a power washer, you just earned a C-minus in the corrosion quiz.

But don’t worry. You have another chance to bust the rust and improve your grade. By the end of class, you’ll be ready to ace the test and save money in the process.

Let’s start with the pressure washing, which was long believed to be the best way to remove salts. More recently, members of the Technology and Maintenance Council reported that pressure drives salts deeper into crevices. Some detected corrosion deep between brackets and mounts. The new thinking is to flush salts after washing, brushing gently while flooding with low-pressure water.

If that’s how you answered the first question, you’re well on your way already. The importance of passing the corrosion quiz becomes evident when we stop to do a little math.

In 2000, a well-equipped Class 8 truck might have cost $90,000 to $110,000. With 10 years’ inflation, that might be $115,000 to $140,000 today.

But something happened on the way to 2010. EPA imposed three ever more stringent emissions regulations. First, exhaust gas recirculation added about $2,000 to each truck back in 2002 with the push-forward mandate of the 2004 emission regs. With 2007 compliant engines, diesel particulate filters added another $6,000.

2010’s selective catalytic reduction systems are adding another $9,000 to the sticker price. Even International’s SCR-free system carries an additional cost of around $6,000.

How much cost has been added for emission controls per truck since 2000?

If you add them all up, the answer is between $14,000 and $17,000.

What could have been a $115,000 to $140,000 truck is now easily between $129,000 and $157,000. Next year, better brakes will add even more cost.

Accountants computing depreciation may disagree, but it would seem to make sense to hold on to any performing asset (i.e., your truck) as long as you can.

In the late 1990s, a villain arose. New combinations of corrosive salts and chemicals that control ice and snow started attacking chassis, running gear, electrical systems, cabs and cab hardware. These electrolytes with water form conductive “paths” between different metals, resulting in electro-chemical corrosion.

What can be done to prevent chemicals from attacking trucks?

Answer: Block the paths.

Copper wiring, aluminum tanks and any exposed metals can corrode. Aluminum cabs on steel chassis are vulnerable. Even a steel bolt can react with aluminum components.

Corrosion occurs in three main areas: wiring; cab and body; and chassis and brakes. No matter where it occurs, it can eventually lead to deterioration and disintegration so that a part or component no longer functions.

The way to prevent this is to inspect, disassemble and clean.

Wiring is highly subject to attack from road spray. The best defense is to use sealed wiring harnesses and coat all connections with dielectric grease available from lighting manufacturers. Grease provides a barrier to protect plugs and sockets from spray.

Most trailers are wired the old-fashioned way, using individual wires from point to point. While less expensive, they are also less durable than sealed harnesses. However, repairs to individual wires are possible without having to replace entire modules. Care must be taken to keep moisture out of any wires or connectors.

Before starting electrical repairs, check for corrosive damage. If any damage is found, clean the area with a wire brush or emery cloth. Neutralize electrical corrosion with a solution of baking soda and water. Rinse and dry thoroughly before proceeding.

Never probe into insulation to determine whether a wire is carrying current. Use a probe only on wire ends or terminals. A tiny pinhole is an open path for spray. Once in contact with the metal, the strands will wick the liquid through 20 feet or more in just a few weeks.

What is that green powdery buildup we see on some wires and connections?
a.   Magic gremlin dust?
b.   Irish coffee creamer?
c.   The corroded
      remnants of good,
      conductive wire?

The answer is C. It’s chemistry, not magic, and certainly doesn’t belong in your coffee.

As corrosion grows, it blocks current flow, making what might have been a 10 or 12 gauge wire work like a 16 or even 22-gauge. It decreases voltage and raises resistance, increasing heat. Left unchecked, insulation melts and leaves wires exposed.

When adding or replacing circuits exposed to spray, form a “drip loop” if possible. Use about 12 to 18 inches more wire than the measured distance. Form the excess into a downward-facing loop so any spray that accumulates will run away from sockets.

(For more on repairing wiring, see the June issue of Land Line Magazine.)

Cab and body
Today’s cabs are made with a variety of non-corrosive or corrosion-resistant materials. Steels are often galvanized. Aluminum oxidizes to form a protective coating. Fiberglass and sheet molding compound are plastics that completely resist corrosive salts, but they can be harmed by ultraviolet radiation.

Waxes made specifically for heavy-duty trucks do a good job of protecting multi-part polymer paints from ultraviolet radiation, but not from abrasion of sand, gravel and road debris. These stone chips or sand-blasted paints open paths for salt spray to attack frames and bodies.

Doors, door frames and cab hardware – including hinges, latches and support hardware – are susceptible to corrosion, especially with different metals close to each other.

When corrosion is found, locate the source. If normal road abrasion is responsible, replacing damaged parts may be sufficient. If the cause is different metals coming into contact, separate the parts with coatings, gaskets or paint.

Be careful if structural fasteners are involved. For instance, when attaching internal door hinges, always use OEM parts or equivalent quality. If they must be torqued to specification, do not overtighten.

Why don’t we spray rust-neutralizing paints directly over rust without cleaning the area thoroughly?

The answer is very important. That paint doesn’t really “neutralize” rust – the rust will remain active underneath.

Chassis and brakes
The Technology and Maintenance Council solves real-world maintenance and equipment problems. In fact, the first place the subject of chassis and brake corrosion, specifically rust, was first seriously addressed was at a TMC meeting. 

Salt spray gets into any crevice it can. When it does, corrosion expands over all of the base metal and weakens it. That leads us to our last question:

How does rustjacking happen on brakes?

Answer: Rustjacking of brake shoes happens when rust grows under linings, forcing them away from their base until they crack from the stress. It can happen in as little as 30,000 miles.

Chassis parts bombarded by road debris are especially vulnerable to rust formation. Inspect any aluminum components such as tanks, hangers and brackets for surface damage. If any damage is found, unbolt the part, inspect it, and decide whether it can be cleaned and made serviceable or whether it must be replaced. If steel body panels are rusted through, have a body specialist weld replacement sections.

Always prime and repaint using OEM-quality two-part paints made specifically for trucks. Avoid automobile-grade clear coat paints without catalyzed base coats.

Keep it clean
If you make corrosion fighting part of your preventive maintenance routine, your truck will continue to be a well-performing asset.

An effective way to prevent corrosion from devouring your truck is to keep it clean, which leads us back to the first question. Remember, it’s all part of the test, so don’t let the pressure get to you. LL