The Choice Is Yours

When it comes to metallurgy and corrosion protection, Mopar is superior to aftermarket products.

When it comes to collision repair on Chrysler, Jeep® and Dodge vehicles, you have several choices for repair parts: Mopar® or aftermarket and salvage parts. While some of the aftermarket parts might fit, are you giving your customer the best parts for their vehicle? And while a Mopar part and a aftermarket part might look the same, and even fit the same in some cases, these two parts might very well be different when it comes to long-term appearance and performance.

Many times the difference is material-related. A Mopar fender meets all Chrysler specifications for fit and finish, as well as those for metallurgy and corrosion protection. On the other hand, the white box fender (made from steel, too) can be made from a substandard grade of steel without the required corrosion protection finish.

We’re going to take a close look at modern sheet metal metallurgy and corrosion protection. We’ll also discuss some tips to repair damaged vehicles to OEM standards. After reviewing this information, you’ll quickly see why using Mopar is the right choice for Chrysler, Jeep and Dodge vehicles.

Body Construction Characteristics

Several types of steel are used in today’s cars and trucks. Let’s take a look at one, the Jeep Commander. First of all, this vehicle, as well as many others, uses HSLA steel extensively (HSLA is High Strength, Low Alloy). Typically, HSLA steel is used for the suspension attaching points, because it increases durability.

Dual phase steel is used primarily for improved impact performance. Side rails and pillar reinforcements are two common applications for this steel. With a yield strength in the range of 90-100 ksi, this material hardens during forming and has weldability characteristics similar to those of HSLA steel.

Among the other characteristics you will find are a greater use of structural adhesives, multiple laser welded panels, bake hardenable steel used in the outer skins of doors and stiffer vehicle structure for improved NVH (noise, vibration, harshness) and better suspension response.

Because improved noise, vibration and harshness (NVH) performance has become a high priority over the last several years, a new type of steel, laminate steel, has been developed specifically to meet this challenge. Laminate steel consists of a pair of steel outer skins sandwiching a viscoelastic polymer (flexible plastic). Figure 1 shows the application of this steel in two locations—the dashboard and the wheelhouse. The polymer layer between absorbs noise and vibration, making the vehicle quieter. Another benefit of this unique steel is that repair procedures are not significantly different from regular steel.

Mopar Collision Parts

The same level of high-grade galvanized sheet metal and protective electrostatic coating used to manufacture your customers’ Chrysler, Jeep and Dodge vehicles is found in Mopar collision repair parts. That stands to reason since Mopar collision repair parts utilize the same quality materials, paints and coatings that are used in the factory. So when your repair is made with Mopar collision repair parts, the parts match the vehicle’s factory paint and come with the same level of corrosion protection as the vehicle did when it was new.

Because generic aftermarket parts often don’t meet these same standards, they might not wear as well over the long haul. Thickness of aftermarket metal is often compromised and many parts are more susceptible to wear and corrosion because their coating standards are not as stringent as those followed by Chrysler. And, material tests show most generic metal parts lack the outer zinc plating. Tests of many aftermarket plastic parts reveal they become brittle and unsafe at low temperatures.

Corrosion Protection

It wasn’t that long ago when rust was the number one killer of automobiles. Remember when it was common practice for a dealer to add rustproofing in order to seal the deal? Nowadays, that has all changed as corrosion protection is used throughout new vehicles.

During the manufacturing process of a unibody car, the factory applies corrosion protection using a specialized manufacturing process. This process cannot be duplicated in body shops. However, you still have a responsibility to apply corrosion protection to a unibody vehicle and to use replacement parts, such as fenders, that have corrosion protection material applied (generic parts might not have such coatings)

This corrosion protection is required regardless of the environment and weather conditions in which the vehicle will be operated. Corrosion damage can literally destroy the structural integrity of a unibody from within. Many corrosion protection systems are destroyed during collision repair operations. Metal finishing, metal working and fatigue can cause the breakdown of many of the corrosion barriers installed at the factory.

Restoring Factory Unibody Corrosion Protection

When making a collision repair, refer to the manufacturer’s information for the locations where corrosion protection and sealants are applied. The application process is usually included with the information supplied with the material, so be sure to read and understand it before proceeding with the repair.

The types of materials used include oil-based materials, wax-based materials, primers and color coats. The most important properties of these materials are adhesion, toughness and resistance to the environment.

The corrosion materials must provide good electrolyte barriers to prevent galvanic corrosion. In addition, the material must be able to penetrate tiny crevices and prevent abrasive corrosion. Finally, the material must be compatible with paint systems since many areas of the car must be treated before paint is applied.Materials containing silicones will cause paint conditions such as fish eyes if applied before the repaired vehicle is painted; therefore, no silicone-based material should be used. As many of the repair areas are accessible before final assembly and painting, non-silicone type materials are a must for this type of application.

When protecting an enclosed area, fog type properties for the corrosion material are a plus. The fog properties make the material much less susceptible to operator error or misapplication. With a fog type material, once the material is introduced inside an enclosure, the fog spreads rapidly and evenly into all areas, including tiny crevices. This type of material does not require direct spray applications to be effective. Fog spray penetration into enclosed cavities requires special equipment, which includes an assortment of wands of various lengths and designs.

Some areas are more effectively treated by a brush application of the corrosion protection material. A good example of one such area is the inner and outer engine compartment side rail area. Brush application to the inside of these areas as individual pieces is easy before assembly. After the parts are assembled, a light fog application can be made to the weld areas and crevices.

Remember, brush-on applications are used before welding and fog in applications are used after welding an assembly together.

Desired Characteristics of Corrosion Protection Material

First of all, the material must displace water in order to prevent corrosion. The material can be tested by spraying water on an open panel, then spraying the corrosion preventive material over the water. The water should be displaced.

Secondly, the material should have a creep capability of about 1/4 inch per minute while drying. This assures protective penetration of pinch welds, cracks, etc. The material should be non-combustible when dry and unable to support ignition when wet.

The material should also have a viscosity which inhibits runs and drips. Overspray on the painted surface of the vehicle should wipe off easily without solvent when wet; with solvent when dry.

Finally, the corrosion protection material should be able to maintain the factory corrosion warranty.