advice on 'repairing' deep scratch on car bonnet

[jkn]

Hi all my old motor got fairly badly keyed a few years ago. The scratch went down at least to the undercoat. I have been pretty lazy about doing anything to improve the scratch, cosmetically or otherwise.

Now however I can see there is a thin streak of rust appearing in the deepest parts of the scratch. I am wondering what the best approach might be to minimise the spread of this.

I don't mind a scheme which is functional, & maybe time-consuming to apply, rather than beautiful. The car is probably only going to last me another year or so in any case.

Thoughts welcome. It's a 2006 Mazda 3 FWIW.

Thanks, J^n

[Martin Brown]

Very little once it has started to rust you have the choice of a lot of work or a quick cosmetic bodge that might last a year or two before the rusting under the paint surface expands again. It is always much easier if you repair things before corrosion and rusting has begun.

Be sure to clean it all very carefully to degrease it before you start.

Two part filler for the scratch (though if was very narrow I might use knifing putty) and sanded to level then base coat clear with retouch. Otherwise retouch along the scratch and T-cut it to look reasonable.

Have you ever done anything like this before?

You need a steady hand to follow a scratch well with a brush and the paint is inclined to thicken rather quickly on warm days.

If you are very serious about looks respray the entire bonnet. Spray painting is not as easy as it looks if you want a good finish. A moments loss of concentration and you will know what orange peel is.

[Andrew]

15 years old. Unless the scratch bothers you, just spray or rub something oily into the scratch to slow down the action of the rust. At that age it isn't going to have any effect on the value of the car.

[alan_m]

Rust converter in the scratch (phosphoric acid - 75%+ ebay) Rub a wax crayon of the same colour as the paint into scratch?

[Vir Campestris]

It won't rust through in that time. You could just ignore it :)

Andy

[Davey]

I had good luck with my wife's car using Vaseline spread over the scratch. Replace every so often.

[Brian Gaff]

Get a new bonnet? However if its not going to last long, maybe you could turn it into a feature. Just paint the sides several colours and make it look like a wreck and you will find everyone will let youthrough. Brian