Rusty cars less safe in crashes

Steel. It’s a versatile material used extensively in modern car construction. Steel does have a downside though, left unprotected, the iron in the metal begins to oxidise forming what we know as rust. As the rust starts to take hold, components begin to corrode and lose integrity. Eventually, parts can fail entirely.

A Swedish insurance company recently commissioned ANCAP’s European counterpart to crash test older, rusty vehicles. The results are startling.

Rust causes weakness in cars

A British crash test laboratory conducted the assessments. Two models were chosen, the first-generation Mazda6 and the Mark 5 VW Golf, both produced from 2003-2008. Engineers selected these cars as they are representative of two different vehicle classes, but also commonly suffer from rust issues in critical areas.

Engineers found that rust causes metal to lose structural integrity and become weak. So an older vehicle doesn’t perform as it did when initially crash tested. This problem is further compounded when you consider ageing models feature fewer modern safety technologies.

Rusting, older car presents 20% higher risk of death

The Mazda6 did not perform well under the test.

In a frontal impact collision, the crash test dummy’s head made contact with the steering wheel after the airbag bottomed out. The dummy then bounced off the wheel into the door upright. The car’s body shell deformed in an unexpected manner and the floor caused lower leg injuries when spot welds failed and separated. Crash engineers noted that a weak floor could allow objects to pierce the vehicle’s underside and enter the cabin, with disastrous consequences.

Over the decade since production ceased, Mazda's sedan dropped from a weak four out of five to a weak three points. In total, it shed 8 points on NCAP’s scoring system.

Researchers concluded that in a heavily corroded vehicle, occupants had a 20% higher likelihood of dying in a crash.

The Golf, on the other hand, performed remarkably, losing only a single point from its original crash rating. This underlines a key finding of the study, that each car rusts in a unique and individual way due to a range of variables, making them unpredictable.

The laboratory tested both cars to the same standards as when new, not to more recent and stringent evaluations.

Identifying rust

Manufacturers apply anti-corrosion paints to crucial components at the factory, but eventually stone chips and wear cause coatings to break down. Drivers living in coastal areas will suffer accelerated oxidisation, thanks to a high salt content in the air. Boats and vehicles taken onto the beach also suffer badly with rusting.

You can identify rust by bubbling, flaky paint and a red/brown pitting. Rust generally starts small but will get worse if left untreated. If you are buying a car, take time to look underneath and examine the condition of structural metal components. If you see ragged holes and lots of loose corrosion, the car may be too far gone.

It’s possible to use a hammer to ascertain the condition of metal surfaces. If you tap the steel and it produces a sharp, defined ring, the metal should be in sound condition. If tapping makes a dull thud, the steel has most likely started corroding.

Preventing rust

Once the rust on a part reaches a certain point, it will need replacing or repairing by a professional welder. You are far better off preventing rust by taking some simple precautions.

• If you drive in seawater or even on the beach, take time to wash the vehicle off with fresh water. This eliminates salt which is a catalyst for oxidisation. Clean the underside of your vehicle too.
• If you spot surface rust (light rust), abrade the surface to remove pitting and flakes, then overpaint with a corrosion inhibitor and anti-corrosion primer/top coat. Look for marine grade products as these often perform the best.
• Greasing nuts and bolts with a non-metallic lubricant can ward off rust and make removal easier. There are also anti-corrosion sprays available.
• If you notice a window, door or seal is leaking, get it fixed right away!

Newer cars are safer

Research shows that newer vehicles are statistically safer. You can use our car loan comparison to find a great deal on a modern car. We’ve also written about Australia's safest cars. Use ANCAP or used car safety ratings to find out how your car performed when crash tested.

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