Do I Need to Remove This Black stuff? (Rust Question)

JCMiller23

'05 Dodge 2500 T1N (fedex)
Trying to rust-proof my t1n as best as possible. I grind off all the rust until I can see bare metal around the wound before applying POR15. The rust spots have a black pitted area that doesn't seem to be able to be ground off easily (with a rust brush attachment on a drill) (See photo: https://imgur.com/UPvwH27). Will the POR15 take care of this?

A friend told me that I needed to get it off completely (probably making a hole in the van) and fill in the gap with a mesh patch and tiger hair. What are your thoughts?

Thanks!
 

hulagun

Haulin' A** since 1974
My thoughts are grinding thru is NOT called for, unless the rust has eaten all the way thru and is blooming on the back side too. But then you will need to seal the back side too. Basically, if you can't push an awl thru the metal (using some force) there, I wouldn't grind it. Just wire wheel it.

Not saying your friend is wrong, but maybe you should go back and read the POR-15 instructions again?

Is that photo before or after after you used the POR-15 Metal Etch treatment? If after, the black should be OK to coat over with POR-15. I'd be worried about any reddish specks that still need to be "converted", tho.

You have to basically kill as much of the rust as you can (even down into the microscopic fissures and pores of the metal) by "converting" it with the Metal Etch. It works better on on smoother rust (no flakes). Apply the acid wash, let it work, then rinse that off with water (I wonder if brake cleaner or denatured alcohol would be OK? It would dry even faster). Immediately after it is rinsed off and dried (use a blow dryer if necessary) apply the POR-15 to seal it in and prevent any moisture from getting to it again.

If you need to smooth the area out after, body filler can be applied over dry POR-15 (scuff it first with a red scotchbrite pad for better adhesion).
 

JCMiller23

'05 Dodge 2500 T1N (fedex)
I haven't opened up the POR15 just yet so this is a before picture. The black stuff is definitely hard and I can't push through it, I just have no idea what it is. It doesn't seem harmful yet, so we'll see how it goes once I have the POR15 on it, I have heard that stuff works wonders. Thank you for your advice!
 

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