What is the best way to prep a large panel, like a hood, that is covered with rust? It's not to the point of pitting, yet, but it's pretty rusty. The paint has burned off so badly that it's turned dusty brown. Are there any products that will prevent rust like this from coming back, or letting the paint get a good grip? Are there any decent rust converting etch primers?
If its not pitted and just surface rust, you should be able to take a DA and some 80 grit and take it all down.
You need to remove rust. Conversion coatings are a "bandaid". I know a lot of people will disagree with me on this point, that's fine, but their wrong If you dont have pitting, then sanding the rust off shouldn't be a problem. Sand blasting (or other "hard" media) gets a bad rap, but if done properly it's still one of the easiest, and best methods of rust removal. I use a pressure pot blaster @ 125 psi max. 70 grit sand (respirator is a MUST) I blast a min. of 12" from the surface, and keep moving. Dont try to take all the rust off in one pass. You can get more agressive in stronger areas, like jambs and edges, less agressive on low crown areas or in the center of panels.
i take rusty sheet metal to a place that blasts with coal slag dust....takes off all paint and rust , with no warping
I planned on DAing it down, but will that be enough to remove all of the rust, so that it will not come back? Should I then etch prime it, and if so, what would be a good etching primer? For spotting, I use SEM's spray-bomb etching primer, but I'm not sure if it'll be adaquate enough for an entire hood.
I think you are going to need to blast it or wipe it down with something that DISSOLVES rust. If you can get the metal squeaky clean with no hints of rust in any pits/pores, then spray it with etching primer. Then use a sandable filler primer to fill the pits in.
I think as long as you dont see any pits or rust you will be OK. Something I have done in the past that has worked for me on areas that I think may have some pits is DA the panel down. Then I bought some of that Extend rust converter. I was leary of useing this and should have bought something better from the paint supply but it was Sunday and Pep Boys was all that was open. I sprayed the questionable areas. After it cures (i think 24 hours) I DA'd back over it just leaving it areas I thought were pitted. I hav'nt had any problems. As far as etching primer. I have just always just used DP 90 followed by a 2K fill primer. My A was pitted deeply in the rear wheel wells so I sandblasted those. It was the first time I had blasted and I liked the results other than the huge mess I had in the driveway.
BLACK 3M SCOTCHBRITE PADS!!!!!!! I get em from my paint supplier, Eastwood sells em. They go on a variable speed 7" grinder. And basically I agree with everything Tinbender said!!!! Do it his way then go to it with the 3M pad.
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