Automotive Study Eyes Corrosion of Body Panels, Underbody Parts

Rust control treatment is applied to an automotive vehicle. Photo courtesy of CNW Group and Krown Rust Control.

Engineering faculty researchers at the University of Windsor (Windsor, Ontario, Canada) concluded that untreated automotive vehicles had 6.8 times more visible corrosion on body panels and underbody parts than vehicles protected with rust control treatments from regional rust protection products provider Krown Rust Control (Schomberg, Ontario, Canada).

The researchers conducted the study on nearly 400 total vehicles in the Canadian province during two separate sampling campaigns. For underbody parts subjected to greater exposure of dirt, gravel, water spray, and road chemicals, untreated cars had 3.6 times more corrosion that those with the treatment, according to the research team.

“The results are statistically significant at a 95% confidence interval,” says Susan Sawyer-Beaulieu, a research associate and post-doctoral fellow at the university. “The chance that these results might be misleading are close to zero.”

Corrosion Index Rating

To measure the amount of corrosion on vehicles for the study, the university’s research team photographed the visible surfaces of 228 treated vehicles that were collected through the course of two sampling campaigns. The results were then compared to measurements taken from 141 untreated vehicles that were collected in a similar fashion. Both treated and untreated vehicles that were studied varied in make, model, and age.

All pictures were taken with a digital camera equipped with a camera-mounted light-emitting diode (LED) light assembly, then manually analyzed by two graduate students using a digital image analysis software package known as Analyzing Digital Images (ADI). Armed with these images, the scientists measured the amount of visible rust with the software to determine what percentage of the surface area in square centimeters was corroded. They then recorded that number to establish each vehicle’s Corrosion Index (CI).

Corrosion on the body panels was identified, measured, and classified according to three different categories of corrosion severity: blistering, surface rust, and perforations.

According to the researchers, blistering is considered the mildest form of corrosion because the paint is still present and offers some protection, although corrosion has started beneath the painted surface. Surface rust is more severe because the protective coatings have essentially failed, and the metal is now corroding. Perforation is the most severe, because the metal has lost part of its integrity in this phase and the perforated area no longer offers any protection. Each category then takes on a different weighting factor in the CI equation.

Corrosion on the underbody parts was all classified as surface rust, because the underbody parts did not have painted surfaces and were thus not subject to blistering. These parts also did not show any evidence of perforations.

The researchers did note that summarizing and interpreting the data all manually using the ADI software was very time consuming, with a range of roughly 5 to 60 minutes required to measure the areas of corrosion in each picture, depending on the severity of corrosion present.

As a result, future work from the research collaboration is aimed at further quantifying the severity of corrosion while also developing a digital imaging and analysis methodology to automate the process of digital image analysis. This, they say, will eliminate any results potentially biased due to the “human factor,” while also streamlining processes and allowing researchers to interpret and statistically analyze more data in a shorter period of time.

Tip of the Iceberg

Sawyer-Beaulieu believes that her team’s study1 only exposed the tip of the iceberg when it comes to the corrosion levels on cars since they only surveyed about 35%, on average, of the visible surfaces of the vehicles they studied. That figure was enough to establish a valid statistical comparison between treated and untreated vehicles.

However, many parts of the car that are harder to get at were not examined, according to the researchers. As such, they warn of the possibility that some of the untreated vehicles are even more corroded than they were able to measure.

The study’s results also confirmed that the effects of not using rust control treatments are even more visible as a car gets older. Researchers observed no significant statistical difference in visibly corroded areas on vehicles up to the age of six years, but from the age of seven to 15 years, the amount of rust seen on untreated versus treated cars jumped significantly.

“Considering that the average age of a car in North America is 11 years old, rust control treatments have the potential to improve and extend the experience and utility you derive from your vehicle,” says Craig Shuttleworth, marketing director at Krown. “What's even more important is to start the treatments early because you don't want to give rust a head start. It can be years before corrosion becomes visible, but by then it could be too late.”

The company, which operates in more than 250 locations in Canada, the United States, and Europe, develops rust inhibitors, lubricants, and penetrants for a variety of end applications.

Other Treatment Benefits

Shuttleworth also notes that keeping a car rust-free makes it safer to operate, especially by protecting the under-surfaces of the car that are rarely seen.

“Corrosion on your vehicle’s underbody may not matter cosmetically, but it can represent a safety issue,” he says. “Specifically, the vehicle frame, which when compromised by corrosion can cause life-threatening failure in the event of a vehicle accident.”

Steve Fletcher, managing director of The Automotive Recyclers of Canada (ARC) trade association for automotive recycling, says the corrosion protection provided through these rust control treatments also has environmental benefits that are often overlooked.

“Corrosion protection not only keeps your car looking good for longer, but it keeps it on the road in good condition for many more years,” Fletcher says. “That’s not only good for the consumer by keeping money in his or her pocket, but it's good for the environment because it keeps cars from being disposed of before they need to be.”

Responsible automobile recyclers, including ARC’s members, are taught to methodically process each vehicle to maximize how much material can be reclaimed from it and to minimize their environmental impact. Unfortunately, Fletcher says, too many vehicle disposal operations simply crush cars to sell them for scrap metal, sending the remaining components to landfill sites.

Source: Krown Rust Control,


1 “University Research Demonstrates the Benefits of Krown Rust Control Treatments,” Cision News Releases, August 16, 2018, (November 20, 2018).

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