Rusty cars on the road are a rarity these days but according to a recent automotive industry report, some modern electric vehicles are surprisingly prone to corrosion.
The car magazine Auto Motor und Sport has cited Tesla's Model 3 as a prime rust candidate, while problems have also been reported with rusty bolts on other Tesla models and the disc brakes of electrics from other brands.
Meanwhile, Volkswagen said it has spent a small fortune on preventing potential corrosion on its ID3 model, which has a 12-year guarantee against rusting through.
Rust expert Ralf Roessler examined a Tesla model with just 300 kilometres on the clock for the automotive journal and he found that the frame had been given only a thin coat of paint. The A-pillars were also filled with a construction foam which absorbs water.
"After six months it will turn brown, after six years it will be completely rusted,” said Roessler. Rust was visible too on the connecting rods of the suspension, said the expert who predicted that the corrosion would spread if left untreated.
Rust on cars has been less of problem in recent decades thanks to widespread body galvanization and underbody protection sealants along with the use of cavity sealing and plastic wheel arch liners.
It appears manufacturers are now saving on overall rust protection and moving to spot galvanizing, said the car mag. The need to save weight because of heavy on-board batteries can also lead to the use of thinner gauge mild steels and materials like aluminium and magnesium which might react and cause galvanistic corrosion.
Corrosion like this can remained undetected for a long time, Marco Oehler, technical manager with the GTue testing agency, told Auto Motor und Sport.
"This happens if unfavourable material pairings are used in hidden locations, which are harder to protect if moisture seeps in during everyday use," said Oehler. "This acts as an electrolyte and corrosion spots can appear inside before they can be detected from the outside."
Volksagen said the sills under the doors of its ID 3 are sealed with wide strips of plastic to avoid them reacting unfavourably with the steel that surrounds them.
The battery box is also made of steel and it also has to be isolated from the aluminium frame to prevent corrosion, said VW's chief bodywork developer, Johannes Neft.
"We do our utmost to ensure that these two metals do not make contact with each other, which is why we have filled the inside of the steel with wax and the cavities in the aluminium sills have been specially coated," said the engineer.
General rust has not been banished from the car world entirely and Germany's huge ADAC motoring club warns that it can pose risks to both older electric and conventional cars.
The rusty rear brakes on the Toyota Prius hybrid and some electrics were caused by the fact that the stoppers are only used in emergencies causing the discs to develop rust owing to lack of use. This is because electrics rely largely on recuperative braking which slows down the motor and converts kinetic energy into power.
"Rust affects the crash safety of a car. Especially when the load-bearing structure is damaged," said Maximilian Bauer, ADAC Vehicle Technology Specialist. "This applies particularly to the sills which are usually the most prone to rust and play a very important role in the rigidity of the passenger compartment.”
Tesla has had problems with rust issues in the past and a recall for rusty steering assist bolts has hit owners of the Model S. Tesla said it has now taken precautions.
Figures show that rust problems still affect a considerable number of modern cars whether they are powered by an electric or combustion motor.
Data collected by the GTÜ technical inspection agency for Auto Moto und Sport showed that of the the 6.66 million vehicles submitted to GTÜ test centres for the main roadworthiness inspection, since January 2020, 441,000 vehicles had rust problems. These were mostly vehicles older than a decade. Of the 3.46 million used vehicles, 435,000 had rust problems (almost 13%) and 357,000 had serious defects. – dpa