Underbody rust spots

[43st]

I changed to my summer tires today (I know I know) and I washed the wheel wells out really well since I had the tires off. I noticed some small rust spots starting on some of the surfaces under the car, just reddish discoloration mostly. I was wondering if there is a reliable method to treat the rust at this stage or is is more trouble than it's worth?

Some background info.. car is a 2004 Mazda3, I live in the North East.

 

[Blain]

Cut > Patch > Prime > Paint

 

[SparkyJJO]

If it is just surface rust you don't need to cut it most likely, just sand it down real good to get rid of it and prime/paint it.

 

[dandragonrage]

When you paint it, you can use something like POR-15 or Zero Rust or Rust Bullet to make damn sure it won't come back in that spot. There's also rubber underbody spray you can try. But the most important thing is to get the surface clean first. (Note: Some people say the underbody spray can trap moisture against the metal and actually CAUSE problems. I haven't used it, so I don't know.)

 

[iamwiz82]

A little surface rust isn't going to affect anything. Any car in the salt belt will exhibit this, it's inevitable.

 

[43st]

Yeah, I'm well aware of the outcome living here.

I was just thinking that if I approached it early I could offset a portion of it. I've noticed that cleaning the car with the clay bar yearly really eliminates spotting from environmental fallout. Which made me wonder if I could do something similar under the car.

I remember a product 10 years ago or so that chemically reacted with rust to make it inert, but it seemed like a gimmick so I never tried it.

 

[dandragonrage]

Rust converter? It kind of works but don't expect miracles.

 

[iamwiz82]

Originally posted by: 43st
Yeah, I'm well aware of the outcome living here.

I was just thinking that if I approached it early I could offset a portion of it. I've noticed that cleaning the car with the clay bar yearly really eliminates spotting from environmental fallout. Which made me wonder if I could do something similar under the car.

I remember a product 10 years ago or so that chemically reacted with rust to make it inert, but it seemed like a gimmick so I never tried it.

You could do the POR15 treatment, but it is a ton of work (three stages), messy, and a bit pricey. I have used it with great success, though. It took weeks to get the spots off of me when I used it, so I highly suggest a full paint suit. I just had a shirt and gloves.

 

[dandragonrage]

Zero Rust is similar and comes in regular spray cans and is also cheap. Rust Bullet is supposed to be the best of the 3 (though I have not personally used it) and I believe comes in paint cans like POR-15.

 

[alkemyst]

Originally posted by: iamwiz82
A little surface rust isn't going to affect anything. Any car in the salt belt will exhibit this, it's inevitable.

QFT...the undercarriage of any car will get surface rust in places...clean it up if you are concerned and hit it with some type of coating.

 

[Juddog]

I used rubber spray on all the non-hot parts on the bottom of my car to make it last longer through the road salt winters here in the NE, seems to do a pretty good job, just don't spray it on the muffler or pipes leading to the muffler.

If you do the rubberized spray yourself, make sure you put on eye shielding, a breathing mask, and rubber gloves, because if it gets in your pores it's very hard to wash out.

 

[halik]

Originally posted by: iamwiz82

Originally posted by: 43st
Yeah, I'm well aware of the outcome living here.

I was just thinking that if I approached it early I could offset a portion of it. I've noticed that cleaning the car with the clay bar yearly really eliminates spotting from environmental fallout. Which made me wonder if I could do something similar under the car.

I remember a product 10 years ago or so that chemically reacted with rust to make it inert, but it seemed like a gimmick so I never tried it.

You could do the POR15 treatment, but it is a ton of work (three stages), messy, and a bit pricey. I have used it with great success, though. It took weeks to get the spots off of me when I used it, so I highly suggest a full paint suit. I just had a shirt and gloves.

POR15 is easy as hell, all you need is their metal prepo solution and a steel brush....

 

[iamwiz82]

Originally posted by: halik

Originally posted by: iamwiz82

Originally posted by: 43st
Yeah, I'm well aware of the outcome living here.

I was just thinking that if I approached it early I could offset a portion of it. I've noticed that cleaning the car with the clay bar yearly really eliminates spotting from environmental fallout. Which made me wonder if I could do something similar under the car.

I remember a product 10 years ago or so that chemically reacted with rust to make it inert, but it seemed like a gimmick so I never tried it.

You could do the POR15 treatment, but it is a ton of work (three stages), messy, and a bit pricey. I have used it with great success, though. It took weeks to get the spots off of me when I used it, so I highly suggest a full paint suit. I just had a shirt and gloves.

POR15 is easy as hell, all you need is their metal prepo solution and a steel brush....

The stains on my driveway 3 years later disagree that there is no more prep work. 😉

This was more my experience: http://www.tidewatermoparclub.com/TECH/tech5.html

 

[earthman]

If you live in the salt belt, it's important to keep the salt off as much as possible, especially when it warms up. Wash it off as soon as possible, especially under the car, and especially if it's in a heated garage. Rust is temperature sensitive, the warmer it is, the faster it spreads. Below freezing, rust happens very slow.

 

[43st]

Ah, great posts here. Thanks for all the comments. I've been rather bad about the car upkeep recently, I really need to schedule regular under body rinses throughout the winter. Spraying water around is usually the last thing on my mind in January though.