There is a small amount of surface rust on my bonnet (maybe 3*3mm), probably from a rock falling on the car.

Is it important to get this removed asap or can we expect it to stay small for a long time in which case no need for immediate action.

I notice lots of old cars have rust under particularly under arches, but I dont hear of rust being a common repair so I imagine small amounts dont really spread to anything significant for years?

2 Answers 2


It will grow; the speed depends mostly on how much of the time it is wet or damp. If appearance is not important , occasionally putting a drop of oil on the bare area will slow the rust substantially. The rust will be progressing under the bordering painted areas.

  • do u mean rust will be progressing under the painted areas, and I will not even notice, or should the new rust push the paint out so i'll see it progressing? Jun 30, 2018 at 1:52
  • would i be right in saying that, generally speaking a few rust spots at the bottom of a wheel arch can take years before it becomes something significant? Jun 30, 2018 at 1:54
  • I expect it will go only a couple mm before the paint will blister and flake off. Jun 30, 2018 at 21:01

It is not fatal.

The bonnet is not a load-bearing structural part of the car. Yes, it will look bad but if you're interested in safety it is not a problem. I don't believe rust in such a location would cause a failure in mandatory inspection.

I would make the decision based on the current value (i.e. age) of the car. If you think the car has resale value, you might want to fix the situation.

If you, on the other hand, will be driving the car until it is scrapped, and don't care about the looks as much, you can perfectly well choose to do nothing.

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