Well my son came over to sandblast some wheels and prime them for his car, so we decided to do some HOW-TO short videos. I hope you guys that want to try some first time spraying get some benefit from these. I will answer questions and I hope some of the other paint guys will add some information as well. This is geared toward do-it-yourself in the garage projects. Even though we are doing wheels, these techniques and products can apply to many small to medium parts and pieces. Keep in mind I'm not a professional filmmaker, but I hope you enjoy the results. If you don't have a small gun you can turn the pattern and fluid down on a big gun, but you need more air pressure to make the big gun work (atomize) because the material is coming through a bigger hole (orafice/tip size). The smaller guns are relatively inexpensive when you buy the copy cat makes and they will usually pay for them selves in material savings.
Here's TomH's wheel painting "barbecue rotisary". It works slick! http://www.jalopyjournal.com/forum/showthread.php?t=62177 Here's the Nason equvilent of the Sikkens etch primer (with filling capability) https://www.oreillyauto.com/detail/...1-gallon-green-etch-primer/nas0/491171?pos=20 Here's the Transtar finish tech primers. They have similar etch primers as well as epoxy and urethane. Click in the product and the tech info. https://www.tat-co.com/TranstarAutobodyTechnologies/media/TATCo/Product Assets/English Datasheets/transtar_tds_6111.pdf?ext=.pdf Here's the PPG Omni 2 part etch primer. https://images.oreillyauto.com/parts/img/documents/ppg/ob60+mp220+chrome+free+etch+primer+09+15.pdf There are basically 2 kinds of etch primer. VINYL WASH SELF ETCHING PRIMER: very little film build (fill) and it is slightly more aggressive, acid wise, because it has only a vinyl resin as the film. You can usually see thru it. It is translucent (very thin) and care should be taken not to apply heavy thick coats. THIS etch primer should be coated with either a primer sealer or primer surfacer (filling primer) before a topcoat/paint is applied usually with a wet on wet system after the etch primer has flashed for 1/2 to 2 hours. In industrial/fleet applications this is usually applied to sandblasted steel or aluminum then sealed with a primer sealer and painted. For restorations it is usually applied to bare sandblasted steel or aluminum and primed with a filler primer so it can be blocked sanded or leveled before painting. This type of etch primer should NOT be used over body filler. Some examples---PPG 1791 etch primer or 171-172 etch primer---Sikkens wash primer CR. MILD SELF ETCHING PRIMER: this has some build or fill but is less agressive acidwise because of the solids or filler in the primer. This can be painted over with some single stage paints without other primers (check the tech info for the brand). It is usually applied to sandblasted steel or aluminum and can be coated with primer surfacer (filling primer) or sealer wet on wet after about 30 minutes up to 72 hours (or longer) with some brands. This type of etch primer is OK over body filler (not heavy wet coats). Some examples--Sikkens Wash primer EM---Sherwin Williams GBP---Dupont Variprime Most companies use the same activator/reducer for both etch primers, which is a solvent blend with about 5% phosphoric acid. The phosphoric acid in the reducer is the "etch" and converts iron oxide to iron phosphate. This my preferred primer for sand or media blasted panels. I usually follow it with some 2K urethane high build primer surfacer (wet on wet). I've used this mild etch on bare engine blocks followed by a good quality single stage urethane color with excellent long lasting results and lots of steel or aluminum wheels. I'm not sure where the spray can/aerosol etch primers fall in here, but I'm guessing more like a thinner version of the milder etch primer. I like them for small parts or touch up on welds, etc. Automotive panels new from the factory have a phosphate coating on the bare steel. When you sandblast or sand the metal on a car you usually remove all or some of this coating. You can replace this factory corrosion protection (phosphating) with a 2 part metal prep acid wash which is messy and time consuming. Although not quite as good, using an etch primer on old sandblasted or sanded steel panels is the closest you can get to replacing the phosphate coating. If you use the metal prep and converting system to phosphate coat panels, you should NOT use an etch primer. It will probably fail and peel off. Several automotive refinish companies require using an etch primer when repairing new car finishes in order for the paint and repair to be warrantied at the bodyshop. Polyester based primers (featherfill-morton eliminator-etc) usually cannot be applied over etch primers, because the acid will slow down the catalyst (MEKP) in the polyester primer and cause the cure to be longer. I did read in the new Evercoat Easy Sand tech sheet, for that brand of polyester primer surfacer, it can be applied over etch primer but it extends the cure time of the primer. You should not use epoxy primers over self etching primers as the acid does affect the activator of the epoxy and can change it chemically so the epoxy may not cure correctly or at all. Epoxy primers DO NOT etch or convert rust/iron oxide. AS always, read the tech info. Most of these companies have good information available on the web or at their local distributor's store, and you can always email or 1-800 a question to their tech dept. As with all good priming systems (epoxy-etch-urethane-polyester-etc) , if you read the tech info,it always says: "The bare steel should be clean of grease, oil, and dirt and free from rust." Here's some info on different types of primers including "WHY" we would use certain types of primers. Look at the "GOOD"--"BETTER"--"BEST" systems on the PPG refinish chart. https://us.ppgrefinish.com/PPG-Refinish/Features/Sidebar/Omni-System-Selection-Guide http://www.jalopyjournal.com/forum/showthread.php?t=182387
Great demonstration with lots of good information. I always thought epoxy primer would protect from rusting. Thanks!
I vote that all of overspray's videos and posts automatically become archived in the tech section or at least pinned on the front page for several weeks!! This is great info!!
I used the etch primer because we sandblasted pretty aggressively and removed all of the original phosphate coating on the metal, and we had some surface rust on the areas to be refinished. The rust was mainly where the rim and the center of the wheel come together. It's very difficult to protect that area from rusting again, but the etch primer is probably better at stopping the rust from "creeping" under the paint/primer film because of the acid converting the minute amount of rust left to iron phosphate. The etch primer was faster and easier than using metal conditioner, not better, but still very good corrosion protection. I put on enough product to give a total film build, including paint, that should protect the metal from corrosion for a long time. Most epoxy primers are "rust inhibitors" along with almost all other metal coatings, including etch primers and even phosphate coatings. Some epoxies are better than others. "Rust inhibiting" basically means it slows down rust. Eventually, all coatings will break down and lose their ability to protect the metal surface from oxidation. Phosphate coating on steel panels has been around for a long, long time. It is the same process you can do yourself using 2 part metal condidioning, and probably the best starting point for bare steel. The metal still needs to be further protected by usually a primer and paint. Film thickness and how well the film resists UV rays, chemicals, and wear will determine how well it protects. The total of phosphate, primer and paint is the total protection. Sanding the bare metal followed by a couple coats of say--DP epoxy is not very good protection. Phosphate coating (metal conditioner) followed by epoxy primer (1.5 to 4.0 mils) followed by a good paint film (another 3.0 to 5.0 mils) is probably good protection. If you use some fill primer for sanding and are doing a base/clear job, you probably end up with even more film thickness and maybe even more protection. Not all primers are created equal. Always read the tech info to see what the dry film build per coat is so you know where you are at for protection. DP epoxy is only about .5 mil per coat, yet a lot of jobs get started with 1 or 2 coats of DP epoxy, and some even stay at that stage (Oh yeah, DP is lead free as are most primers produced today) so they don't protect as good as they did years ago). Using DP as a foundation for a high build is a better way to protect the surface, or you can check out some other primers (epoxy or other direct to metal) that have more solids and film build per coat to increase the protection. Plan the job by researching and reading the tech sheets and build a system for your paint film. Most of the paint companies have already put these systems together so all you have to do is look it up on the net and read the info. Stick with brands and systems that are readily available in your area. It's easier to get support and more product when you run short.
I have a newly assembled engine that I would like to paint. It has some rattle can and some good paint on it with no indication of adhesion issues. Any tips on prepping this for another paint? A color change is in order, but I want to be careful not to harm any part of the assembly with abrasives or their byproducts.
Well we ended up with spray can lacquer (from the Camaro parts vendor) so we went ahead and used it. So lets continue this with some "spray can body work tips and techniques". Please feel free to add any and all spray can technical info. We all use them, even the "pros". The drawbacks are: No temperature control with faster or slower solvents. No air pressure control. Very little film build per coat. No spray pattern or fluid adjustment control. Only a few spray cans have a "fan" type spray nozzle. They are---CHEAP---EASY---DISPOSABLE. On with the "Hillbilly" chrome job.
The Jalopy Journal
