hi all, it'll be my first time to do body work and I have a few questions.I have scrolled back the last 20 pages and got more questions then answers . lol. I got some rust over my rear quarter panels and want to fix it. I have my paint codes as its two-tone.What is etching? Thought I could just sand,clean, bondo if needed, sand more,prime and paint.Its a 95 F-250 4x4.Its just a work truck, not for show , but I do want to keep it up as best as I feesably can. Any input is appreciated. Thanks Bob

 

etch primer is a primer that will etch and bite into the metal and will take care of fine flash rust. It has phosporic acid in it. They also make metal preps that are similar that have phosphoric acid but are wiped on the surface. If you have sanded and clean metal free of rust, or you have phyxically removed it, there would really be no reason for you to use an etch primer. Etch primer should not be painted over, and you need to use another primer over it. There are also strict warnings on many of them, about using over or under bodyfiller, not very compatable with polyester resins. It also is a 1k product and is solvouble by solvents. Its use has really been going by the wayside for most cases.
Just make sure you cover any exposed metal asap, as flash rust can start forming due to moisture and humidity in the air, and anything thats been blasted it begins forming quickly. Try to get metal covered by the end of the day, but if it has sat for more then a day, I'd resand exposed metal prior to priming. You should use a primer that is direct to metal type, and epoxy primer is about the best, cause it will not be porous like other primers, sealing off metal from air and moisture. It is also very compatable with most other products, and sticks well. Unfortunetly most epoxy primers don't have a lot of fill for bodywork areas and blocksanding, or sand easily. Most use a urethane filler primer or if extreme fill is needed a polyester filler primer over epoxy for blocksanding things straight, filling scratches, and ease of sanding. You can paint over urethane or polyester primer, but sealing everything when bodywork is finished with epoxy primer reduced is a sealer will have its advantages if you don't mind spending the extra money. Only would really need a coat or two. You should finish the scratch in your bodyfiller and metal down to 80 or 180 grit before priming. How many rounds of filler primer and blocksanding really depends on how straight things are.
By all means if your existing finish is in good shape and a catalyzed or factory finish, you can sand and paint over it, which it should be with your truck. You can test by taking a rag soaked with lacquer thinner and see if the finish softens or you can remove it. If it doesn't you are pretty safe. But sometimes it is best to get the vehicle all one color with a sealer (epoxy reduced also makes a good sealer) if it will help with coverage of your new color, or you have a lot of different colored primer spots you would need to cover with your paint and as extra insurance.
If you only have rust around the wheel wells, I'd grind that area down to baremetal. If it is weak or has holes, you really should replace the metal if you want it to last. Physically remove rust from any pits by blasting or using a 3m course brown scotchbrite disk. You should be able to buy a small spot blaster reasonably priced if you don't have one, and just need to clean up some pits. You can then epoxy prime to protect and seal the metal and use bodyfiller or 2k finishing type filler over the epoxy primer for filling low areas or pitted metal , and don't even need to sand it prior you are still in its window, which is usually a least a day or two. Epoxy priming then using bodyfiller over the next day seems to work well. Any other primer or over paint, you can use a 2k spot or filler primer over after sanding in moderation. I wouldn't do a large area or too much thickness. Regular bodyfiller is not recommended over paint. You can also bodyfill over sandblasted or ground metal, but always nice to have that epoxy underneath protecting things (make sure you blow off metal after sandblasting and wipe with wax and grease remover if its been touched at all by finger prints, reblow off and allow wax and grease remover time to evaporate if used). You should never fill in rust holes with plastic filler. Fiberglass filler or mat and resin may last a little longer, but still don't give repair long if holes are filled. Replacing metal is the only way to go. Don't forget to make sure to try to treat the backside of rust repairs also. Stick with 2k primers, fillers, and paints and if you did your repairs well, you should have a long lasting repair. Avoid lacquer primer or the spot putty that comes in a tube and doesn't require a hardener. But with 2k paints and primers, it is very important that you protect your lungs, eyes and skin when using and have adequete ventilation. Its is also important since they cure chemically to keep the metal temperature above 60 degrees when applying and for several hours afterwards. Also if a media is used to blast that contains any silica, the fine dust it creates is very hazardous to inhale. Always protect yourself when doing any blasting also. Not trying to scare you, but this is a field where saftey is important, and you protect yourself and take necessary precautions. Better to be too safe then not safe enough using materials that are flammable or explosive and can affect your nervous system and organs. Get the product data sheets for the primers and paints you plan on using, as they will give you a lot of good information about them. Most basecoat paint you should final sand with no courser then 320 dry by machine or 400 wet for solids or if sealing and 400 dry or 600 wet for some metallics. It should be stated in the product data sheets for the paint you use, so check that and follow the recommendations.

 

thanks for the info. I am gonna get the things together and work on it this weekend and see how things turn out. I do appreciate the great insite you gave me on this ,Bob

 

I started some of the work on my truck today, wow, its a lotta work. thought it was gonna be kinda simple. Guess I owe the people who do body work and paint an 'atta boy". no wonder its so expensive to put in the shop.