Waxed Chassis Rust Prevention

[AmericanPie]

I own a 2020 GMC Sierra 2500HD gas 4x4.  As with all GM trucks of this type, the chassis was dipped in wax to protect it from corrosion, however over time, some of this wax peels away ( or is chipped away), then surface rust appears.  Left unchecked, the surface rust takes over, and the next thing you know, you're looking purchasing a new truck.

 

Two questions: 

1.  What methods are used to clean and stop the surface rust?

 

2.  What products are used to recoat the chassis following the removal and remission of surface rust?   Is there a compatible wax undercoating available from Bodyshop supply houses, or do we simply use off the shelf spray can undercoating (will it stick to the wax)?

[Grumpy Bear]

19-NA-255 1..10 (nhtsa.gov)

 

OR

 

PB Blaster Surface Shield after a quick wire brush of the bare area. 

Edited July 21, 2023 by Grumpy Bear

[jaxcam02]

This isn't exactly the correct product but it's all I have laying around but I use bearing and axle grease and pat it on the bare spots. You can buy aerosol cans of the factory wax but that ****** is like 60 bucks a can.

[Gangly]

Daubert NOX is with that manufacturer uses.  I purchased a few spray cans of the stuff when I purchased the truck, and I use it occasionally to touch up parts of the frame where the vehicle lift contacts it.

[AmericanPie]

Even if we recoat the chassis with the correct wax type product, we still have the issue of surface rust and how to deal with it.  

 

My initial thought is to power wash the chassis to eliminate any contamination, especially from road salt.  Even then the bare metal has residual oxidation that must be removed or chemically converted.  There are many OTC products that will work, but my experience is they're only asgood as your chassis is free from road salt.  If you coat with brush on latex or Permatex spray type rust converter, over road salt, you actually make it worse by locking in the Oxidizer. 

[Z45]

When does this become an "exercise in futility"?   

Edited August 19, 2025 by Z45

[Bikerjon]

4 hours ago, Z45 said:

When does this become and "exercise in futility"?   

Definitely is.

[Joe Drives]

PB Blaster Surface Shield I used on a rusty Jeep frame. I did not do any preparation, and a year later still had good coverage when it was sold. Recommend reading the MSDS and using personnel protective equipment regardless of the product chosen. 

[Gangly]

First this...

 

 

 

 

 

 

 

Then this...

 

 

 

 

 

Then apply the OEM wax coating...

 

Edited August 22, 2025 by Gangly

[davester]

You are doing something wrong if your roll bar gets anywhere near 250F.

[Paul Beaudet]

Krown rustproofing, every year.

[EXSlider400]

I use Fluid Film and in black…but try sell clear as well. 
 

https://www.amazon.com/Fluid-F80-AS11B-11-75-Aerosol-Lubricant/dp/B08WRMLPCG/ref=sspa_mw_detail_multi_sbb_img_m_sccl_1_1/138-9516956-0122857?pd_rd_w=suZLb&content-id=amzn1.sym.d42cefb2-fcdb-4dd6-bbdf-2aa4ef1ab24f&pf_rd_p=d42cefb2-fcdb-4dd6-bbdf-2aa4ef1ab24f&pf_rd_r=JC8NQXDP0QBKME212GAC&pd_rd_wg=oFxxi&pd_rd_r=13c75b1a-212d-4837-9f4f-12a533613cfd&pd_rd_i=B08WRMLPCG&psc=1&sp_csd=d2lkZ2V0TmFtZT1zcF9waG9uZV9kZXRhaWxfdGhlbWF0aWM=

[kickass audio]

I tried 3M cavity wax on my old 2014 Silverado and it didn't help with crap, probably because it was too late when I bought it after it was a lease and the rocker rusted through on the passenger rear at the bottom and the rear wheel wells were rusting through even though I flush them constantly and use the wax coating on it.

 

My current 2023 is nice and clean and only has a tiny bit of surface rust on the very front upper frame area where it's hard to reach for having it coated and I take it to rustkote for undercoating every fall before winter and it's been doing great. I also pull the wheel liners in the summer and fully clean the liners and the steel then wax it with carnuba wax and touch up on the cavity wax for any edges that are hard to wax. I do have to pay each year for the cavity wax but i'm not happy with the work i've seen done at krown and ziebart.

 

Rustkote does a great job for me with coating the bottom and inside the doors and rockers, my only complaint with them is they spray the inside of the engine where the cross brace and frame at the top by the radiator sits and it makes a mess of overspray and I just take a old oil rag to wipe up the excess on the plastics. They also try to wash the overspray on the body but it doesn't work and I always take the truck home and hand wash it to get the excess off the body panels and glass. You can hand wash but can't flush the underside and even where I live, the carwash doesn't have any underspray like they advertise so it will never flush the underside out.

[Black02Silverado]

AMSOIL's Heavy Duty Metal Protector works great for an undercoating or even touch ups.  I use it on my 2019 Silverado. It doesn't effect the factory coating.  If you want a quote for a couple cans let me know.    

 

https://www.amsoil.com/p/amsoil-heavy-duty-metal-protector-amhsc/?zo=521390