I don't see any reason to coat the aluminum. The e-coating on my 2015 still looks brand new, and the truck spent it's first three years in Canada's rust belt.

 

I didn't do my 2020 when I bought it new and I regret it. My rear axle was a mess, so I treated it with a rust remover acid, painted it with rust reformer, then coated it with CRC Marine Heavy Duty Corrosion inhibitor. I'm planning on doing the rest of the frame and suspension in the next week or so with CRC, but I'll sand and paint the few rust spots first. The CRC is basically cosmoline so it dries and isn't tacky like fluid film. I'll fluid film some of the concealed areas though, like the spare tire winch and inside the frame cross members.

 

Your truck looks great! I spent 3 winters in VT and know how heavily they salt the roads. I had brought my Toyota truck from AZ.
I used to spray it off underneath about every other week. The second year I noticed a bunch of rust developing, especially around
the wheel wells. Thinking about it, I was probably “pushing” the salt further into the frame. Was able to sell it before moving back to AZ.
Rusty vehicles don’t sell well in AZ. LOL.

 

It's not for the aluminum. It's for the steel frame and suspension. Boxed frames are very strong but can trap dirt and water inside the frame, which rusts the frame from the inside out. Not to mention rust is ugly and makes vehicles look old or uncared for. I'm trying my best to make my '15 the last truck I purchase.

I will add that aluminum body parts sometimes start to corrode from rock chips, the edge of the stamping, or from under trim. Hopefully the 13th gen F150 is better than past Al efforts, but if I do see it on my F150, I'm going to try to stop it by dripping linseed oil into the scab or seam.

 

I was responding to Bassman150 who said he Krown coats the underbody.


CRC MHDCI dries immediately. Cosmoline takes about two years. Like fluid film, cosmoline will need to be replenished annually, while the CRC product should only need annual attention to direct spray areas.

 

Is the CRC stuff anything like Amsoil HDMP? I used the latter in years past. It’s good and holds up well, but doesn’t seem to creep and get into tight places like WW and FF.

 

I've never used any Amsoil product, but someone here probably has.