Do you need underbody rust protection on new Prime?

No smell. sponge brushes work good. I'd agree a spray is a lot easier, think linseed oil would tend to gum up any kiind of spritz bottle. Suprisingly good though: a year later, through one winter, it's protected good.

 

Maybe rust-mort is similar. I've found that locally. Still, it seems like brushing off anything loose, and then applying a tenacious sealant, is quite effective.

 

Exhaust systems have been upgraded to be more corrosion resistant over the past 15 years or more. All used to be made of mild steel and rusted away readily within 3-4 years. The roads and highways used to be lined with muffler shops.

Now, the muffler shops are gone, in that most all exhaust systems come from the factory with 410 or even better 304 grade stainless steel.

Most all erstwhile muffler shops do brakes, oil changes and suspension work.

The aftermarkets replacements are not always stainless steel but mild steel to keep the price down for the consumer. If you plan to keep the car for a long time, OEM replacements are your best option.

Short trips are also a killer of exhaust systems, because condensation bearing corrosive acids are not "burned" off.

 

Exhaust systems I would just clean it, if you're under there and ambitiously cleaning. Maybe spray around those grommets with silicone spray, but avoid overspray onto the main exhaust pipes.

My main targets (3rd gen) were the suspension components, large framing pieces, especially the weld zones, the shock absorber joints, and the big bolts.

Those were the items that were rusting like crazy after a few years.

 

So........... am I in the wrong to just use a touchless car wash once a month (it does the undercarriage), instead of rust proofing? That seems like a lot of work.

 

Rust is caused by the marriage of water and metal left exposed to the air over long periods of time. The colder the air, the longer the exposure. In your case, the once a month car wash is helping in non-cold months, therefore keeping rust down. But doing it in the winter may excelerate rust. I would buy that stuff that Homedepot sells and spray once a year. Hopefully this is helpful for you.

 

Car washes do not use clean city water. They filter and recycle the old stuff. There is no way to filter out salt except by expensive distillation or reverse osmosis.

So, I would not go to any car wash during the winter salting season. Biological dust and debris also holds salt water and electrolytes between metal parts and promote rust.

The key to rustproofing is to coat the spaces where metal contacts with metal or plastic to form a layer of protection.

 

Exhaust systems rust from the Inside Out much quicker than from the outside in.


Rob43

 

There's nothing you can do about that at any "reasonable" price point.

Any type of spray, lube, or coating just won't work because of the heat that's involved. As mentioned by Georgina Rudkus in post #44:
"Short trips are also a killer of exhaust systems, because condensation bearing corrosive acids are not "burned" off."

This corrosive condensation is collecting Inside your exhaust where you can't see it. If you've ever seen/followed a car (ICE) at start up, you probably remember the tail pipe spitting what looks like liquid out of it. That liquid is all the condensation that build up from the last time the car was parked, it was sitting inside the exhaust system doing its dirty work...Rust.


Rob43

 

Agreed. There are many conflicting factors in designing and manufacturing an exhaust system. The thickness or thinness of the metal is determined by the weight of the system and the gas mileage burden as well as the cost of the metal. In the current incarnation the reduction in weight is offset by using more corrosion materials usually stainless steels. 410 grade is apparently used as it is economical but not totally as corrosion resistant as higher nickel and chromium bearing austensic alloys like 304 or 18-8.

All stainless steel alloys corrode in high heat oxidizing environments. Outside browning and surface corrosion is apparently only visual and not damaging.

Thicker metal parts in the exhaust system are usually not stainless steel to save money. In all but heavily salted road environments, it is not a problem. Unfortunately, it is in your area. Other than machining and installing stainless steel equivalent replacements, there is really no solution.

Replacing standard plated steel fasteners with stainless or titanium nuts and bolts would be helpful, if they are available in the sizes required. Dissembling fasteners and coating the threads with 2500 degrees plus anti-seize lubricants would help and allow saving some components, if not all, when future service is needed.

 

"IF" this ever becomes a real problem for you, you could look at lower mileage crashed/auto recycler Prius Primes from areas that don't use salt on their winter roads. It's might be possible to find a suitable replacement for ~50 cents on the dollar, if that time comes.


Rob43

 

So true. I worked with a guy that lived about 2 miles from work. I think he replaced his muffler every couple of years if not more frequently.

 

I can't help but go back to my guaranteed solution for rust (whatever the heck that is!!): move to Southern California!!
I'm sorry, but I couldn't resist!!

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I think the biggest rust issues I've seen under my cars are some of the bolts. Might be good to spray some Fluid Film on them once in awhile.

 

3rd gen rear suspension joint:


Same joint, the bolt head:

Shock bolt:

And this is a low miles car, on the wet coast, about 3~4 years back.

Same location as above pic, about a year since linseed oil application:

 

For exhaust systems, disassembling the nuts and bolts and coating the threads with this anti-seize lubricant might help. Since it withstands temperatures of 2400 degrees F, it might be used to coat bare mild steel components.