Corrosion protection at Volkswagen: Twelve years in “fast forward” mode

Corrosion – commonly referred to as rust – is the enemy of all cars. That makes protecting against corrosion vital when it comes to value retention, safety, customer satisfaction and, not least, the image of a company. For decades, Volkswagen has been consistently applying corrosion protection measures to ensure high product quality. Corrosion protection starts long before production – in fact, it is designed into each new vehicle model from the outset. Months before and after production ramp-up, future vehicle models undergo comprehensive tests on a special proving ground and in the lab to simulate all the stresses a car goes through in its life in a short period of time.

Volkswagen also recognises that many of its markets around the world contend with particular stress factors for cars, be it salt, dust, frost, heat, humidity or silt. That is why the Group employs dozens of corrosion protection managers in 14 countries of its production network. At every site, corrosion protection is teamwork that requires close collaboration between the Development, Production and Quality Assurance departments as well as coordinated, comprehensive tests.

Series monitoring is another important instrument. This involves employees in Quality Assurance performing spot checks by removing vehicles from ongoing production in order to subject them to the same gruelling corrosion test.

In vehicle production at Volkswagen, corrosion protection has five pillars: seal seams, cavity sealing, paintwork structure, galvanisation, and anti-chip coating and underseal. “We have been performing corrosion protection in the modern sense for more than 40 years,” says Dr Johannes Neft, Head of Body Development for the Volkswagen brand. “In that time, we have not only continuously developed new solutions, but also retained tried-and-tested technology. One example of this is the wax flooding of the body in white which we have been doing since 1978.” In this process, the painted vehicle body is preheated to 80°C and cavities are briefly flooded with liquid wax at 117°C, which applies a thin layer of wax that offers permanent corrosion protection.

However, corrosion protection starts long before production – in fact– it is designed into each new vehicle model from the outset. For example in the doors of the new Golf: Doors are referred to as wet areas into which rainwater enters from above and drains out below. That is why Volkswagen applies no less than three protective measures in the lower section of the door, where the interior and exterior parts meet: a technical adhesive fills the cavity and thereby securely joins the two parts. A polyvinyl chloride seal seals the folded edge, and the interior areas of the doors have water-repellent industrial wax applied for cavity preservation.

Volkswagen has developed an innovative underbody design for its purely electric ID.3. The large high-voltage battery is located beneath the passenger compartment and is protected from below by an aluminium sheet. The sheet represents the core of the completely encapsulated underbody. Its plastic covering not only protects against corrosion but also considerably improves aerodynamics beneath the vehicle, thereby also increasing its range.

If the ID.3 should sustain a side impact from another vehicle, the hybrid side members protect both the battery and the occupants. To reduce the weight, the side members are fitted with lightweight aluminium profiles on the inside and extremely lightweight yet ultra-high-strength steel is used. Even though the hybrid side members are dry areas, targeted corrosion protection measures are still applied here: the cathodic dip coating lines all cavities, while the inner sides of the sheet metal panels are additionally protected by wax flooding.

Volkswagen uses this range of tests and measures to secure the longevity of its models around the world – since no rust is not the norm.