How to save Sonata engine cradle from rust?
 

I have been extremely lucky to get a 2000 Sonata that appears to have a rust free engine cradle and lower control arms. After reading about the rust problem, I decided I should do something to keep it that way, because it is a wonderful car, and I want it to run forever!

I high-pressure blasted the underside, drilled a 3/8" drain hole in the back of each side of this "C" shaped engine cradle, then sprayed it, and the lower arms, with black "Rust Reformer" spray paint.

But I am concerned about the inside of this engine cradle, since it is a closed, welded, assembly, I would like to treat it inside somehow, does anybody have any good methods for this? Also should I drill a drain hole in each lower control arm and treat the inside too?

I hesitate to take it to the dealer, because I am low on work and can't afford anything they may add to the bill, even though they have a recall campaign for this.

Thanks for your advice.

Well, I find a number of treatments, some say that I need a coating of rust, and it will reform it, some say it will work on clean surfaces and it will protect it, some are water soluble, some say must be free of water.

I suspect there could be some rust in there, maybe water, so the only thing that seems appropriate is CorrosionX HD, which says it is for marine applications and will coat the metal even if there is water on it.

Anybody have experience with this?

There is a marine paint, POR-15, that is as tuff as nails. I've used it on a couple of cargo trailers. It may be worth a shot.

Jim,

Thanks for the response, I will look into POR-15. The toughness will be great for the outside. I am also concerned about the inside, as it is a captive space between the upper and lower halves that are spotwelded together.

I understand from other research that salty water gets inside (the "drain" hole is in the front) and does its dirty work unnoticed. Mine has lived for 10 years in North Dakota, no salty water, so I was not surprised to see good solid metal when I drilled a drain hole in the back on either side. Now it lives in S.E. Mich with plenty of salty water. I want to treat the inside, but cannot clean the surface first, or even see it to know if it is in the proper condition for whatever treatment I want to use.

Yeah, I lived in Rapid City for a while... minimal use of salt. Indianapolis just throws tons of the crap down, and even starts to spray the streets with a liquid salt-brine mixture hours before the snow even starts.

Getting creative with a length of plastic or vinyl tubing and a make-shift 'spray' tip out of copper tubing may do the trick. Pull the tubing into place thru the cradle, attach the tip & as you pull the tubing thru nice & slow, find a way to pressure feed your paint/coating into the enclosed cavity..... it can't hurt.

Sounds like an excellent method, I could use my pump-up lawn sprayer to provide the pressure, and even if I had to "flood" the thing, I could recover the excess out the drain holes and recycle it, maybe strain it first.

I believe the lower control arms are built the same way, and I could do them too.

I looked up the POR-15, and they also have a metal prep for the surface before coating. I think it would be best on the outside, because it has a hard coating that seals out moisture. And CorrosionX HD on the inside, as it requires no surface prep, and will displace water if there is any.

Thanks for the help.