Preparing a vehicle for the spraybooth isn’t like heaving a bowling ball down a lane, intent on hitting something. It’s more like carefully tiptoeing toward something — in this case, a final product that’s properly cleaned, sanded, stripped, masked, primed and sealed, flaw checked and, finally, positioned in the booth.
How can you be sure your prep staff is carefully and thoroughly prepping vehicles for painting? Consider the following basic, yet essential, tips to properly prep a car for the spraybooth.
A Clean Machine
Washing the vehicle should be at least as important as setting up the spraybooth. It’s recommended that you:
• Pressure wash the under-chassis and wheel-well areas.
• Clean the door- and trunk-hatch jams.
• Clean under the hood with hot water. But be cautious of water that’s too hot. Steam may be ill-advised because of possible damage to critical computer sensors or other sensitive electrical and electronic components.
• Use the very best wax and grease removers you can. And remember, silicone from wax will kill any paint job from the very start if you’re unable to get it off the surface before painting.
• Clean the tires and wheels. The really dirty part of an automobile starts with the tires and wheels. To clean them, remove the tires and rims, and scrub them down in a wash-rack area.
The wheel covers should be taken off, washed and stored after cleaning is completed.
Be sure the specific area you’re about to work on is washed with a soap solution that will get down into the pores of the metal or primer surface. Don’t use a simple spray-on/hose-off technique. Put some muscle into it. In a lot of cases, a chunk of a Scotch-Brite pad will do a good job getting off the deep-down grime.
• Blow off the vehicles with clean, dry compressed air to finish the cleaning process. This is effective in extracting dirt, pollen and other potential contaminants from small, confined areas that aren’t accessible with a rag. You can also use microwave drying equipment.
On the Surface
Once the cleaning phase of the vehicle prep is complete, re-inspect the surface, especially those areas that will be refinished. At this point, metal techs should have already completed any pulling, dolly work or straightening. The prep tech’s job now should be to scrutinize the vehicle to make sure fit and finish will come together when the vehicle rolls through the spraybooth doors. This includes checking out the previous finish for fading, dulling, checking, blistering, spotting, bleed-through, cratering or other related problems, such as the effects of acid rain.
When dealing with an old, withered finish, don’t fool around. Take it down to bare metal to achieve the first step in a perfect foundation for paint. Shops that have been around more than a few years all have horror stories about paint jobs that lifted, peeled, blistered, wrinkled and turned to garbage either right away or within a few months of the final application of the topcoat. You don’t need me to tell you this is a costly mistake. But I can tell you that correct prep can make all the difference.
Chemical stripping can make short work of correcting a blotched or withered finish. As you go through the paint-removal process, remember that rinsing the base metal is critical. Some prep people live by sand or bead blasting and apply the process to every car they can. But the blasting procedure, while effective at removing paint, can leave residue and dust. It can also mar a finish that’s already been partially or completely scrubbed down.
To avoid such unwanted results, use blasting equipment with proper dust-recovery equipment attachments and be selective about when you use the technique. Corrosion that’s started into the surface finish would be a likely candidate for the use of blasting.
Sanding, grinding and orbital stripping using a heavy-grit paper are all good surface-removal tools. Use grinding when small, flat areas are to be worked on. Also, grind the unevenness out of curved sections that disturb body lines. Orbital sanding should follow any grinding process and will do a good job on metal scratches. In such cases, use 80-grit paper for the best results.
Make it Stick
Ten years ago, well before high solids came to be, metal prep was done hodge podge. Some shops used an etching chemical, while others depended on wiping agents — or just the primer and sealer themselves — to provide good paint adhesion.
Times have changed and, today, the absolute best way to ensure a successful paint job is to:
• Start metal prep with a wax-removing agent.
• Mix metal prep with water to create a solution that fits the finish you’re working on. A good rule of thumb is that the rougher jobs should be mixed “hotter,” or stronger, but not in such strength that a film is obviously left behind while using an abrasive pad.
• Use the correct and compatible conversion coating on the affected areas. An abrasive pad will help work the coating into pores and tight areas of the surface. Five minutes is good enough to cause the zinc phosphate chemical base to form. Rinse off with a solid stream of water, but avoid high-pressure stuff from here on in.
Panel Replacement
Prep work also involves a lot of panel replacement. The primer coat on the body part you pulled out of the box is a non-identifiable substance (You didn’t put it there, did you?) as far as I’m concerned. Because of this, it’s important to scuff, re-seal and/or re-prime the part with your own paint-system compatible product. You haven’t come this far to go down in flames because of a few bucks worth of primer. Adhere to the same drill as always — de-wax first, then scrub and treat the panel with metal conditioner just as if the part had come to you with no coating. Continue the process and finish sand as required.
Guiding Your Way
A “guide coat” should be applied to the refinishing surface before the vehicle heads into the spraybooth. A guide coat is a very thin coat of quality primer used to bring all the imperfections to a level of visibility to highlight any flaws. The flaws may exist because of contrast, shadow markings, and minor highs and lows left over from metal work. Without this guide coat, a painter’s work would be curtailed rather quickly by problems that surfaced with the first undercoat or, worse, while spraying the topcoat.
Off to a Good Start
Though the steps I’ve walked you through don’t revolve around new, high-tech procedures, they’re all very important. Hopefully, your prep tech is already incorporating them into his daily routine. If so, you’ve established a quality base for successful paint work and efficient use of your spraybooth. If, instead, you’ve consistently seen poor results in the paint booth, you may want to review the above steps with him. Following the above tips won’t guarantee a flawless finish every time — but they will guarantee a solid start to a stunning and long-lasting paint job.
Contributing editor Bob Leone, a retired shop owner, is ASE Three-Way Master Certified and is completing qualifications as a post-secondary automotive instructor in the vocational school system in Missouri.
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Faster Isn’t Always Better Phosphoric acid contained in the reducer of certain wash primers will act like an etching agent. Like older self-etching primers, the metal prep and primer application are simply combined into one step. My experience here leads me to lean toward the older two-step process. The reason: Critical areas that need more work than others would be denied the extra attention necessary with a “one swipe and we’re done” philosophy. |
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An Insider’s Look Ever wish you could take a peek in one of those mega-shops, just to see what they were up to? Ever wonder if their prep techs know something yours don’t? Well, here’s your chance to sneak a peek. I toured Reliable Toyota, Lexus, BMW’s Collision MegaCenter in Springfield, Mo., to get an inside look at a dealer-run super shop. I’d already heard great things about the shop’s VOC compliance and efficiency levels, but I wanted to check out the prep department for myself. Though the shop is still relatively new and long-term production levels haven’t been calculated, collision director Chris Butcher figures the prep and final detail departments work at 130 to 140 percent. How do they do it? • Equipment — A fully equipped wash rack with hot- and cold-water capability is the first step in prepping for the spraybooth. After washing the vehicle, Butcher says it’s common to dry it with compressed air using a special nozzle. Microwave drying equipment is also used when required. Reliable’s two heated downdraft prep stations are perfectly aligned with two state-of-the-art spraybooths. This setup allows for prep work to immediately precede production paint work. Drying is done in prep stations or, more efficiently, in the dual environmentally controlled downdraft spraybooths. • Setup — Reliable’s prep area is located in the last third of the assembly-line-like arrangement the shop uses to advance work. It’s set up so one car is always waiting after the wash rack to enter one of the two prep booths. One car is always in each prep booth and one car is always in each paint booth. A waiting and inspection area between the prep and paint booths is a “catch all” quality-control area where vehicles are OK’d to proceed or rejected because of ineffective masking, undercoat problems or other reasons. A similar area that can accommodate two to four cars and is set up for buff-out and detail work is located after the paint booths. • Methods — Butcher noted that Reliable’s prep techs probably work much the same way techs in smaller facilities work but did offer a few tips that have helped to make the shop’s prep area productive and profitable. — Wash the car completely before it’s delivered to the prep area. Completely, says Butcher, includes the inside, the outside and the under structure. This prevents dirt from contaminating the job at hand, as well as the next one or two that roll through the prep booth. — When vehicle repairs are scheduled, allot definite amounts of time for clean-up, prep work, refinishing and curing. Though time is, of course, part of overall efficiency, Butcher says quality is the only benchmark that will get the vehicle out the door. |
