peej410 Posted March 8, 2003 Share Posted March 8, 2003 i just cleaned off sanded to bare metal and primered my inner fender on one side i plan on using rubber undercoat. i bought some bluemagic jet spray pure rubber undercoat.. should i paint the inner fender first then apply the undercoat or can i spray it over primer? also which way will the undercoat adhere better? i tried doing a search and i got nothin.. thanks... pete Quote Link to comment Share on other sites More sharing options...
Guest thinkmonkey Posted March 8, 2003 Share Posted March 8, 2003 The problem you may run into is the underbody rusting out underneath the undercoating if it is not specified to inhibit rust. Datsun undercoated the z's (sparingly though) on the bare metal and then painted over, which eventually rusted out when water got underneath. I'd recomend a good etching prime on the bare metal, or maybe a coating of por15. -David Quote Link to comment Share on other sites More sharing options...
peej410 Posted March 8, 2003 Author Share Posted March 8, 2003 hmm well i have por 15 but i chose not to use it because i dont have the metal ready or the other thing you have to use. i was told those were required is this true? Quote Link to comment Share on other sites More sharing options...
drunkenmaster Posted March 8, 2003 Share Posted March 8, 2003 if it is clean metal you need the metal ready but it is not very expensive. The marine clean i was told is not necessary, and wax&grease remover will do. Quote Link to comment Share on other sites More sharing options...
peej410 Posted March 8, 2003 Author Share Posted March 8, 2003 alright, cant paint POR over primer though correct? Quote Link to comment Share on other sites More sharing options...
Guest thinkmonkey Posted March 8, 2003 Share Posted March 8, 2003 Well you can but it defeats the point. After you por15 you want to either ruff it up with some sanding or use their proprietary primer before you undercoat/topcoat. -David Quote Link to comment Share on other sites More sharing options...
peej410 Posted March 8, 2003 Author Share Posted March 8, 2003 so por-15 doesnt end up a finished surface? Quote Link to comment Share on other sites More sharing options...
Guest thinkmonkey Posted March 8, 2003 Share Posted March 8, 2003 Sort of. After you apply it and it dries it's a smooth surface that will take abuse like nobody's business, even though it flows out really well and ends up fairly think. You can even reshape the metal afterwards with a hammer and it will still conform. The problem is that when exposed to sunlight (uv spectrum) it changes color to, I think, brown. It still works after that, but the fact that it breaks down in sunlight means you should probably topcoat it. Primer has some trouble sticking to it, so sand it before you prime or use their proprietary primer. Or undercoat. Once it's on though, that area is not going to rust unless it rusts from the other side. I'm coating my whole underside and inner rockers, then spraying in rustoleum/rust tough to get in any cracks. Following that for really intricate areas I'm also spraying in some rust mort just in case, then using primer to seal up the area. When priming over the por-15 with rattle can it needs to be sprayed on thin at first to 'get some stick.' My self etching stuff runs more because it is somewhat corrosive. Sandblasting would be better, but it is messy. I did most of my car sandblasting but it is very annoying to do and even so there will still be rust in there hiding somewhere like the inner rockers. -David Quote Link to comment Share on other sites More sharing options...
peej410 Posted March 8, 2003 Author Share Posted March 8, 2003 yeah i hate sandblasting always getting shit allover the place... my garage floor has like 10 lbs of sand on it... the previous owner tarred the whole car. man id like to break his jaw. had it not been for the fact that Zs are hard to come by up here then ida bought a cleaner car... o well , thanks for the advice ill try it - pete Quote Link to comment Share on other sites More sharing options...
drunkenmaster Posted March 8, 2003 Share Posted March 8, 2003 im about to start removing all the underbody sealant/tar with and anglegrinder and wire wheel attatchment. after that it will get a coat of POR15 and then some new underbody deadener. I have been told that you can apply a topcoat directly over por15 after 3-4 hours when it is touch dry but still tacky. if you let it dry completely you will need to rough it up and/or tiecoat. Quote Link to comment Share on other sites More sharing options...
peej410 Posted March 8, 2003 Author Share Posted March 8, 2003 if your gonna use a wire wheel and an angle grinder be prepared for that tar to fly all over the place i completely ruined a pair of shorts and a shirt to the point that they werent even wearable for car stuff anymore (their original purpose) id suggest heat and a scraper sand blasting works well for the corners, once u get it down to the point where u have a very thin streaky layer still on there go to yer local pepdudes go to the autobody section and look for a little black wheel that looks like a webbed plastic. stick that in one of your drilles and a strippin you will go. it works pretty well. remember to get at least a particle mask for all the sanding - pete Quote Link to comment Share on other sites More sharing options...
Pop N Wood Posted March 8, 2003 Share Posted March 8, 2003 This stuff has come up before. I think it was RacerX warned everyone about undercoating bare metal. You have to treat it first. Try a search to get the specifics. Also for removing the old undercoating and/or tar the two suggestions I liked best were 1) use a pressure washer, preferably one that heats the water first. Suppose to make quick work of things. The second one was oven cleaner. But you had to use a specific brand to get good results. Quote Link to comment Share on other sites More sharing options...
peej410 Posted March 8, 2003 Author Share Posted March 8, 2003 damn, two things i hadnt thought of, what should i search with ? i tried undercoating, undercoat and a bunch of other things and nothing came up unless it wasnt posted in paint and body Quote Link to comment Share on other sites More sharing options...
Pop N Wood Posted March 8, 2003 Share Posted March 8, 2003 http://www.hybridz.org/phpBB2/viewtopic.php?t=11383&highlight= http://www.hybridz.org/phpBB2/viewtopic.php?t=11281&highlight=oven+cleaner With switch to the new software, all the old links got killed. The second link above contains a link to the pressure washer idea, but it no longer works. Quote Link to comment Share on other sites More sharing options...
peej410 Posted March 8, 2003 Author Share Posted March 8, 2003 thanks jim that answers alot of questions. the second link did work. now my only problem is the fact that my car has no wheels on it and its cold as shit to be spraying anything with water lol... that and the fact that ive already replaced my floors so my drivers side inner fender and my whole rear deck underside area is of concern, i also am doing this without a rotisserie. in the front their is no rust at all however in the rear rust has broken through in alot of places do you think something like ospho will work on the rust well enough ? i want to por15 the whole underside im not spending too much time on the inner fenders because after inspection the front end is getting a tube job (sounds kinky haha) ive been thinking about getting a second Z and trying an approach that scares most (more so then what ive done so far) and building myself a fully tubular frame completely ripping out the old undercarriage and starting fresh hehe , anyways back to topic thanks for all your help ill take lots of pics while im in the process -pete Quote Link to comment Share on other sites More sharing options...
Guest thinkmonkey Posted March 8, 2003 Share Posted March 8, 2003 Funny, Jim linked to my question I asked way back in June. What I ended up doing was the heat treatment and scraper, then washing down with laquer thinner. The stuff that was left I attacked with aerosol paint stripper and it all was gone. AND NO ROTISSERIE! -David Quote Link to comment Share on other sites More sharing options...
peej410 Posted March 8, 2003 Author Share Posted March 8, 2003 yeah i dont have a heat gun only a torch what did u use for heat? i used aircraft stripper and that did a nice job only if you get it on your hands itll eat right through yer skin. i wish i was dealing with actual undercoating.. but mine is just tar so it comes off as disgusting GOO anyways time to get crackin thanks again Quote Link to comment Share on other sites More sharing options...
Guest thinkmonkey Posted March 8, 2003 Share Posted March 8, 2003 You can use the torch if you are careful not to warp the sheet metal underneath, which can really ruin your day. Just cover a small area and lightly heat up the undercoating until it will scrape off. A heat gun mounted scraper can work also, but heat up the general area with the torch first.. -David Quote Link to comment Share on other sites More sharing options...
peej410 Posted March 8, 2003 Author Share Posted March 8, 2003 alright cool thanks Quote Link to comment Share on other sites More sharing options...
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