Removing Magnesium Chloride From Undercarriage

Sorry, but a little bit of a vent before I get to my question...  Just got home (Colorado) from Tucson after trading my 2014 2350 for a used 2022 2552 at La Mesa RV.  I'm very excited about the new coach!

Long story, but after assuring me last Friday, that all parts had been received, and repairs would be complete by the end of that day, it turns out that the "Delivery Team" had failed to order parts to accomplish the "due bill" for the items that were noted when I made the transaction a few weeks ago.  As a result, after my 9:00am delivery walkthrough on Monday morning, and noting the "due bill" had not been accomplished, I finally received the motorhome at 7:30pm.  That leads me to the reason for my post.  I set up the earliest available delivery on Monday because I had a commitment in Colorado on Wednesday morning (today) and needed to leave Tucson on Monday afternoon, to beat a snowstorm that was forecast to begin in Colorado on Tuesday afternoon.

After the delay in delivery, I had to spend the night in the La Mesa dealership parking lot.  I left shortly after 5am Tuesday (yesterday), when they opened the gate, and drove 14 hours straight to get home.  The last two hours were in a snowstorm at night.  About 90 minutes from home, a snowplow pulled onto I-25 in front of me and immediately started dispensing rocks.  Yep, not sand, but gravel with what looked like 3/4" diameter rocks, resulting in at least 3 window chips and perhaps paint chips, but I don't know yet.  They also use magnesium chloride on the roads in Colorado and although I needed to vent a little, that is the real reason for my post.

The magnesium chloride in Colorado has an additive to make it "sticky" and it certainly does stick to vehicles.  It is also more corrosive than salt (sodium chloride). Once it warms up next week, I will remove it from the body with soapy water and a sponge/rag.  Simply pressure washing does not remove it.  Removing the mag chloride from the undercarriage is more challenging.

I've read that you can apply a solution of one part vinegar, one part water, and let it sit for a few minutes before rinsing.  I have a pressure washer and am thinking I'll get a water broom/undercarriage wash attachment and use it with the vinegar mix.  I'm a bit concerned about spraying with too much pressure because of things like wires going to the HWH levelers and spraying up into the battery compartment, etc., but not sure what else I can do.  I'm curious if anyone has any other suggestions for the undercarriage - thanks!

I wouldn't use vinegar... That's acid.  Here's what CDOT usrs

https://www.codot.gov/travel/winter-driving/products

Just water should be fine

I wouldn't use vinegar... That's acid.  Here's what CDOT usrs

https://www.codot.gov/travel/winter-driving/products

Just water should be fine

I appreciate the link.   I realize vinegar is an acid, but the recommendations I've read say to use it diluted, let it sit a few minutes, then rinse to remove the calcium deposits left by magnesium chloride.  However, I've just seen this recommendation in general and not specifically for an undercarriage.   Perhaps it is a bad idea for an undercarriage.

I've never been able to remove magnesium chloride completely from the paint on my car when using just a pressure washer, even if I use the "soap" mode first.  It always leaves a residue if I don't wipe with a sponge or rag. Perhaps, the minor residue remaining would not be corrosive to the metal and rubber on the undercarriage.

Hi Bob,

I am sorry to hear about the rock damage on your new PC.  That would "dig" on me too.  I can only offer empathy, no practical advise.  Let us know what you end up doing for the undercarriage cleaning.  There is so much to clean which is why I have avoided driving in any kind of wintertime weather to-date.  Or PC comes out in late spring, and gets put away in mid fall specifically to avoid road chemicals and salt.  We need our PC to last 35-ish years, this being one practice to help get there.  We are coming up on our 15th anniversary this June, with 20+ years to go.

Hi Bob,

I am sorry to hear about the rock damage on your new PC.  That would "dig" on me too.  I can only offer empathy, no practical advise.  Let us know what you end up doing for the undercarriage cleaning.  There is so much to clean which is why I have avoided driving in any kind of wintertime weather to-date.  Or PC comes out in late spring, and gets put away in mid fall specifically to avoid road chemicals and salt.  We need our PC to last 35-ish years, this being one practice to help get there.  We are coming up on our 15th anniversary this June, with 20+ years to go.

I appreciate the sentiment Ron!   I really didn't want to drive in those conditions, but with the delay receiving my coach, it became unavoidable.  Congrats on keeping your coach for 15, going on 35 years!  We've wanted a 2552 since we started RV'ing 8 years ago, but until recently, did not have a covered storage space that would accommodate.  Our new (to us) 2552 is awesome!  We've named it "The G4," which stands for Giant Gray Gas Guzzler.  That way, I can tell people I own a G4 (https://readyjetgo.medium.com/the-gulfstream-g4-private-jet-7dad5dad48bc). 

I grew up in Colorado and all I remember on the roads, "back in the day," is sand - which apparently, they don't sift anymore, because they were dumping gravel last night.  I can deal with the rock chips in the windshield, but I hope the paint is ok.  It is -7 this morning, with more snow forecast, so I'm not going to check for a day or so.

They use a number of different products, but the worst is the magnesium chloride - I think Colorado started using it in 1996.  Most of the car washes around here (of course none that I could use in my RV) advertise undercarriage washes with formulations specifically for magnesium chloride, but unless they apply something slightly acidic, let it sit (none of them do), then rinse, I suspect it is nothing more than high pressure soap and water.   I've never been through a car wash that has fully removed mag chloride from the body of the car with just high pressure soap and water - as I mentioned it requires a brush, sponge, or rag.

Until I can get more info, I think I will just take Don's suggestion and spray underneath with lots of water, perhaps soap first, and inspect after it dries.

 

Mayb a high pressure steam gun with  a wand?

https://www.amazon.com/Moongiantgo-Temperature-Pressurized-Hand-held-Controllable/dp/B08C9LVDD6/ref=asc_df_B08C9LVDD6/?tag=hyprod-20&linkCode=df0&hvadid=459434176255&hvpos=&hvnetw=g&hvrand=12738265145046044339&hvpone=&hvptwo=&hvqmt=&hvdev=m&hvdvcmdl=&hvlocint=&hvlocphy=9031626&hvtargid=pla-947796867720&psc=1

https://trid.trb.org/view/642605

Study done on corrosive of sodium chloride vs magnesium chloride by CDOT which shows that in our arid state, sodium chloride is worse for coorsion.

There is no calcium involved and as noted before, CDOT includes a corrosion inhibitor.  Just plain water for underbody wash is fine.  Modern automotive/truck frames and bodies are built to withstand the corrosive effects and most manufacturers now warrant vehicles against rust through for 10years or 100,000 miles, whichever comes first.

To be honest, just driving in the rain will work fine... Although it's snowing now here on the west Slope.

My memory is mag chloride used by CDOT is harder on the underbody "rubber" parts like bushings and Seals because it tends to harden them.

Here's an even better link on cleaning it off

https://www.summitdaily.com/news/does-magnesium-chloride-corrode-car-components/

https://trid.trb.org/view/642605

Study done on corrosive of sodium chloride vs magnesium chloride by CDOT which shows that in our arid state, sodium chloride is worse for coorsion.

There is no calcium involved and as noted before, CDOT includes a corrosion inhibitor.  Just plain water for underbody wash is fine.  Modern automotive/truck frames and bodies are built to withstand the corrosive effects and most manufacturers now warrant vehicles against rust through for 10years or 100,000 miles, whichever comes first.

To be honest, just driving in the rain will work fine... Although it's snowing now here on the west Slope.

My memory is mag chloride used by CDOT is harder on the underbody "rubber" parts like bushings and Seals because it tends to harden them.

Here's an even better link on cleaning it off

https://www.summitdaily.com/news/does-magnesium-chloride-corrode-car-components/

Lots of good info again Don, thank you!   I did see the CDOT info on the corrosion inhibitor added to the "anti-icing brine," which they use before it snows, but I didn't see mention of it added to the "de-icing magnesium chloride" mixture, that they use after it snows. Plenty of stories of corrosion make me think not - but I'm not sure.  I doubt the HWH levelers have any anti-corrosion coatings, so that is my main concern, along with rubber fittings and perhaps any "untreated" add-ons (battery tray, power step, generator mounting bracket, macerator, etc) from custom chassis work done at the factory.  Just read a post on here by someone whose leveler actuators were ruined by corrosion from cold weather road treatments, but I think he didn't wash underneath right away.  Your comment about magnesium chloride having no calcium makes sense - I read some confusing articles that referenced the deposits left by mag chloride and I guess I misinterpreted them, but oddly many still say to use an acid based mixture.

In the Summit Daily article you linked, they said this..."But like Stiglich, Bergman said mag chloride sticks to vehicles and water reactivates its corrosive qualities.”You can’t wash it off because it has a bonding agent so it sticks to the road,” he said."  As I've mentioned, I've never been successful just washing off mag chloride, unless I also use a sponge/rag.  Also, plenty of conflicting data and anecdotal stories on which is worse, sodium or magnesium chloride, and why, but I guess that really isn't too important to me. I just want it off.  Perhaps I got lucky and only encountered the non-corrosive anti-icing brine.

Having said all that, thank you again and I'm just going to wash it with my pressure washer and see if any residue remains.

Mayb a high pressure steam gun with  a wand?

https://www.amazon.com/Moongiantgo-Temperature-Pressurized-Hand-held-Controllable/dp/B08C9LVDD6/ref=asc_df_B08C9LVDD6/?tag=hyprod-20&linkCode=df0&hvadid=459434176255&hvpos=&hvnetw=g&hvrand=12738265145046044339&hvpone=&hvptwo=&hvqmt=&hvdev=m&hvdvcmdl=&hvlocint=&hvlocphy=9031626&hvtargid=pla-947796867720&psc=1

Great idea!  I happen to have a steam cleaner - hadn't thought of that and will try it if a simple pressure wash doesn't work!

Our son lives outside Detroit. Local shops offer a service to clean that sort of stuff off the undercarriage of your car. I’m not sure what products they use, but maybe some research for some of those places would help?

Our son lives outside Detroit. Local shops offer a service to clean that sort of stuff off the undercarriage of your car. I’m not sure what products they use, but maybe some research for some of those places would help?

I appreciate the suggestion!  I've been trying to contact local shops, but since temps are still sub-zero (we broke a 123 year old record yesterday!), none of the businesses that might do that (seems like very few here equipped to handle an RV) are open.  It is supposed to warm up into the low '60s next week, so I hope to get it taken care of next week - either by me or a business I can trust.

Without any personal experience, just what comes to-mind.......

If our PC was full of salt and road chemicals, on the first weather-permitting day, I would setup my 3400 psi pressure washer, (always use cold water to protect the pressure pump), attach the white-fan-spray tip, and try to hit everything underneath, every nook and cranny from every angle possible, making sure to get close enough without being destructive.  The wide pattern of the white tip reduces the PSI, lowering the risk of high pressure damage, as well as offering better coverage for "blind" under-chassis spraying.

What would be interesting is first applying with the black tip, whatever recommended chemical is best for lifting the contamination prior to pressure washing.

Here are the pressure tips that I think are now "industry standard" for pressure washers, including THIS 3400 PSI PRESSURE WASHER that I bought from Farm & Fleet last year on sale for what I recall was just under $400.

Curses, mag-chloride!
I have a hot water bib in my driveway. I hook a regular lawn sprinkler and hose to it spread under the vehicle and slowly drag the hose from one end to the other. Repeat a few times and it looks good, and you stay dry.