Best way to remove cement/mineral deposits from Black Vectra?

[salty]

I parked my Black Vectra in an underground car park and left for a restfull nights sleep. Returning next morning I noticed that rainwater had seeped through the concrete roof-slab and dripped on the car leaving 2 inch diameter white stains on the bodywork.

The deposits are stuck pretty solid, thumb mail will not shift it and anything harder scratches the bodywork.
My guess is the deposits are cement powder and other soluble minerals which have dried/etched onto the bodywork.

Anybody know how to shift this stuff without resorting to a jack-hammer????

[spennny]

I parked my Black Vectra in an underground car park and left for a restfull nights sleep. Returning next morning I noticed that rainwater had seeped through the concrete roof-slab and dripped on the car leaving 2 inch diameter white stains on the bodywork.

The deposits are stuck pretty solid, thumb mail will not shift it and anything harder scratches the bodywork.
My guess is the deposits are cement powder and other soluble minerals which have dried/etched onto the bodywork.

Anybody know how to shift this stuff without resorting to a jack-hammer????

Have you tried claying your car mate, i did this to mrs spennny's mini and it was fantastic, mcguyers clay (spelling)

http://cgi.ebay.co.uk/MEGUIARS-QUIK-...1%7C240%3A1318

see it here, give it a good wash and then clay it

[parapaul]

Yep, that gets my vote too - clay with LOTS of lube.

[Wilco]

sorry couldn't resist, have a bash with some clay and as said before use LOTS of lube.

[ANDY W]

Might sound stupid but have you tried a good soapy wash as where I live used to be a building site and there was always cement dust in the air and concrete etc on the roads but all I needed to do was wash the car

[Little John]

It all depends what it is. Probably cement based so there are a few options.
Bilt Hamber Surfex will remove cement,
You can also dab the mark with white vinegar it will remove cement also. It works by atacking the lime and it is a slow process but works take your time with it and don;t go rubbing at the surface or you will scratch it.

But as cement is lime based it most probably will have eaten in to the clear coat and etched the surface of the paint so will need polishing after to remove that, polishing with abrasives not a glaze or wax

Clay may work if it isnt cement but I would expect it to be, if you have clay already then give it a try but I would go with vinegar as you can get it in asda.

[salty]

Some good ideas, many thanks.

Started with the cheapest option, white wine vinegar. Took a lot of rubbing but it shifted it in the end without damaging the paint.

Regards

[tonyord]

there is a concrete car park near me wich has closed recently because too many claims were going in for paintwork on cars due to rain water going through the structure and damaging paintwork you might be better having a word with the people that own the car park as they should pay you to get it sorted as they were doing close to me hope this helps