# Salt/road grit corrosive?



## bellissimo (Jul 28, 2009)

My car is covered in the salt used for the roads amongst other winter contaminants from the road. 

Are there any long term effects of not removing the salt from the bodywork or wheels? Is salt corrosive? I don't plan on washing the car until after New Year but wasn't sure about leaving the salt on the bodywork for that long. Can literally see streaks of the stuff all over the bodywork.

I did an Autoglym wash, Dodo Juice Purple Haze wax, and an Autoglym spray sealant on the alloys about 2/3 weeks ago.


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## hibberd (Jul 5, 2006)

Very corrosive....


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## Avanti (Jan 17, 2006)

graycar said:


> My car is covered in the salt used for the roads amongst other winter contaminants from the road.
> 
> Are there any long term effects of not removing the salt from the bodywork or wheels? Is salt corrosive? I don't plan on washing the car until after New Year but wasn't sure about leaving the salt on the bodywork for that long. Can literally see streaks of the stuff all over the bodywork.
> 
> I did an Autoglym wash, Dodo Juice Purple Haze wax, and an Autoglym spray sealant on the alloys about 2/3 weeks ago.


The car won't disintegrate overnight, however there is no harm in rinsing the muck off

Had this yesterday 









to this


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## steveo3002 (Jan 30, 2006)

hell yeah...its the worst possible thing you can leave on your car

rinse it all off asap once things warm up


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## bellissimo (Jul 28, 2009)

Avanti said:


> The car won't disintegrate overnight, however there is no harm in rinsing the muck off


Any harm done by leaving it uncleaned though?


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## steveo3002 (Jan 30, 2006)

its a corrosive...make up your own mind

like he said...it will still be there if you dont wash it , but over years the car will suffer worse than one thats washed alot


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## mac31 (Dec 5, 2009)

mine has been the same way for the past 6 weeks or so just cleaned it off today doesnt seem to have done any damage to the paint.


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## Avanti (Jan 17, 2006)

mac31 said:


> mine has been the same way for the past 6 weeks or so just cleaned it off today doesnt seem to have done any damage to the paint.


Once the layer is there it can't really get worse, but the car looks so much better cleaned and it can be rinsed in minutes that is the only way but to keep it rinsed :thumb:


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## TOGWT (Oct 26, 2005)

*Road Salt*

Although dry salt is inert 15 - 20.oF (9 - 29.oC) is considered the lower limit for salt to melt snow and ice but once H2O, even in the form of moist air (i.e. humidity) is added the freezing point is lowered and the sprayed brine solution used on roads will have an adverse effect (the formation of rust and/or corrosion) on the vehicles paint and undercarriage. When washing the vehicle ensure that all salt removed to avoid a brine solution remaining on the paint finish. Using a durable protection (Collinite Insulator Wax) will provide a sacrificial and renewable protection to the vehicles paint finish.

The salts (salt CI and water H2O produce oxides, which cause corrosion) used for freezing point depression in a sprayed brine solution (often mixed with grit / sand for tyre adhesion) commonly used are;

(a) Sodium chloride (NaCl) the most common salt used Sodium chloride (rock salt, halite) lowest practical temp: 15.oF (9°.C) keeps sidewalks dry, corrosive, damages to concrete and vegetation

(b) Calcium chloride (CaCl2) works at lower temperatures than sodium chloride. Lowest practical temp: 20.o F (29. °C) melts ice faster than sodium chloride, attracts moisture, surfaces slippery below

(c) Magnesium chloride (MgCl2) is the name for the chemical compounds and its various hydrates MgCl2 (H2O) x. These salts are typical ionic halides, being highly soluble in water. Melts ice faster than sodium chloride. Lowest practical temp: 5. °F (15°.C) attracts moisture

Magnesium chloride is very effective even at the lowest temperatures but also contains the most aggressive corrosives (especially on glass surfaces) and a sprayed brine solution, it is used to prevent snow / ice adhesion to the road surface. A number of state highway departments throughout the United States have decreased the use of rock salt and sand on roadways and have increased the use of solutions of magnesium chloride (often called "liquid magnesium chloride") as a de-icer. Magnesium chloride is much less toxic to plant life surrounding highways and airports, and is less corrosive to concrete and steel (and other iron alloys) than sodium chloride.

Anti-icing liquids, which according to State authorities, the liquid solution consists of - Magnesium chloride (MgCl2) Calcium chloride (CaCl2) and other liquids that work like anti-freeze, by lowering the freezing temperature of water and preventing ice from forming a strong bond to the road

*Corrosion*
_[: Water has a low electrical conductivity, but this increases significantly with the dissolution of a small amount of ionic material such as sodium chloride. Sodium chloride CI and water H2O produce oxides, which in turn cause corrosion] _[1]

Rust (Oxidation) _[:electrochemical oxidation of metals in reaction with an oxidant such as oxygen] _[1]

Needless to state a sprayed brine solution is corrosive; so once you've removed the ice / snow it may be advisable to remove the residue and apply a protective coating, especially on the undercarriage and suspension. Once heat is added to the brine solution (i.e. parked in a heated garage) like any chemical attacking a surface, temperature will dictate reactivity (acceleration of a chemical reaction by a catalyst [moisture and heat].

*An extract from one of a series of unbiased "Detailing Technical Papers" © TOGWT ™ Ltd Copyright 2002-2009, all rights reserved​*


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## Spoony (May 28, 2007)

Someone just brought Science to the party! Woop woop! 

Great post TOGWT


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## Typhoon (Nov 1, 2008)

Sensible countries use ground shale... 

They spread it (salt) round here, then the roadsweepers clear it up, then they spread it again then it rains and washes it away...just before it freezes.... duh!


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## Guest (Dec 21, 2009)

graycar said:


> Any harm done by leaving it uncleaned though?


I don't want to sound awkard (again) but 99% of the british public are hardly cleaning their cars at the moment. Yes it is no good for the car but as Avanti said, it's not going to disintegrate overnight, or even in a month, not even in a year. If you care for your car, get it off when it's next conveniant for you, but don't get worked up about it on for a couple of days.


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## Phil H (May 14, 2006)

keep it as clean as you can, this is the major benefit of a foam lance and some snow foam. 10 mins and a quick pressure wash just to keep on top of it


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## goo (Oct 10, 2009)

It IS corrosive but it depends on how long you reckon on keeping the car. If you buy new every few years then don't worry too much about it as it's unlikely to rot away before you sell it. Just hose/wash it off when you get the chance :thumb:


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## Guest (Dec 21, 2009)

goo said:


> It depends on how long you reckon on keeping the car. If you buy new every few years then it's unlikely to rot away before you sell it :thumb:


Very wise words...


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## alexf (May 23, 2009)

true true, 

but us classic owners do have to worry a bit more. 

Luckily the golf is dripping in waxoil and soon dynax too, 

best bet is definitely to wash it off as soon as really


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## SportWag (Jul 22, 2007)

When I drove Vauxhalls (Astras, Tigras & later Omegas) I found the chrome effect plastic badges started to corrode after a just a few days if the car was left caked in road salt - esp the later models with the Chrome effect Griffin. I had to keep the badges clean when it was too cold to wash the car.


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## David 1150 (Jun 6, 2009)

Have a look at any motorcycle which has been ridden through winter without the salt being washed off, or a protective layer applied, to see what salt does to metal. I've ridden various bikes through winter and all have survived unscathed because I _always_ washed the salt off with lots of cold water before garaging the bike.

I had a 2 year old KTM 640 which I rode all year, then sold it for a Blackbird. It was back in the dealer 4 years later looking exactly as I'd sold it - either it'd been cared for or garaged through winter. Sadly I saw it again 1 year later and the poor thing was so eaten by rust I wouldn't have had it given.


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## qwertyuiop (Jul 3, 2009)

I wash my bikes/car twice a week,salt rots everything, especially underneath where the paintwork is often damaged/neglected and the suspension/brake/drivetrain are exposed.


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## bellissimo (Jul 28, 2009)

*sigh* Looks like I'll be getting the buckets out on Xmas day then.


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## Typhoon (Nov 1, 2008)

graycar said:


> *sigh* Looks like I'll be getting the buckets out on Xmas day then.


Like you would have to think that was wrong....:thumb:


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## RedUntilDead (Feb 10, 2009)

Its not only corrosive, its abrasive too!!! especially if you have to swerve out of the way of the oncoming grit wagon which is travelling at speed in the middle of the narrow road and you then hit the curb with your nearside front alloy as a result:wall:
I have only had the car a flippin week

Si


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## Alex_225 (Feb 7, 2008)

This is why I'm so glad the Megane get's to stay in the garage over winter. With the intention of keeping it for a long time I'm glad I don't have to worry about getting the salt and crap off it. 

Having said that I own a 2002 Lupo and I doubt the previous owners have washed it or protected it like I have in the 18 months I've had it. Yet it's not got any rust anywhere on the car and the underside is tidy too. 

I'm not saying that the road salt isn't bad for the car but as said it's not going to eat away at your car withing weeks.


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