[Dubz]

Around my rear wheelwells on my rear quarters i had a small amount of what appeared to be surface rust, but under further examination was rusted from the other side (sandwiched with the wheel tub). I cut out both peices, and welded in a new face and kitty haired overtop to get back the feature line. Now i was thinking about sandblasting the inside and spraying undercoating or rockerguard or something similar. Would this be the best way to keep the patch from rusting again? or might there be a better way?

All my other patchwork has been from on panels that are open on the other side, so this is new to me.

Thanks for the help guys

 

[gypsypoet]

Unless you cut the entire rusted section out, it will rust again, even under paint. If you did cut it all out (I assume so) then go ahead and spray it, I've never seen good metal rust under a coat of Krylon flat black in my entire life. Rockergaurd will work the same, the idea is to keep water and air from direct contact with the metal.

 

[Dubz]

Unless you cut the entire rusted section out, it will rust again, even under paint. If you did cut it all out (I assume so) then go ahead and spray it, I've never seen good metal rust under a coat of Krylon flat black in my entire life. Rockergaurd will work the same, the idea is to keep water and air from direct contact with the metal.

would sandblasting the backside where it started rusting be a good idea before undercoating? the chances of having got 100% of the rust are never that good right?

 

[gypsypoet]

Like I said, if you cut it all out, you'll have nothing to worry about. Sandblasting is iffy for rust removal, but can work. If you're not going to have to pay for it, I'd say go ahead, but I'd personally have to pay so I probably wouldn't. So long as you cut about an inch away from all the rusted areas (you can go less, inch to be safe, basically so long as you cut all the rust out you'll be good) and you repaired it as you said, you should be golden.