Auto Service World
Feature   September 1, 2008   by Cindy Macdonald

Waterborne paint demands FLAWLESS PREP

Following proper procedures has never been more important, because the thin skin of waterborne basecoat won't hide any flaws.

One of the most crucial differences between waterborne paint and older technologies raises its head before any paint actually touches the car: the nature of the coating means anything less than a meticulous prep job just won’t cut it.

When a bodyshop begins using waterborne basecoat, the repercussions reach the prep department in the form of higher expectations rather than new equipment purchases. “If technicians are following good practices, there won’t be much change,” says Jeff Ford, technical services manager with 3M Automotive Aftermarket Division. But preppers may have to raise the bar a bit in terms of their performance. “Waterborne basecoat forms a tight film, so if the surface prep is not done well, it will show up.”

Given the demanding nature of waterborne coatings, there are a few supplies and procedures that should be considered when stepping up to a waterborne paint system. The masking tape and paper need to withstand the high water content of the coating, without losing adhesion or allowing water to penetrate and lift the masking. Many facilities are also turning to dust-free sanding, either with a central vacuum system or with self-generating vacuum sanders. Because waterborne coatings are more sensitive to dust, it is advisable to keep the facility much cleaner than you might have in the past.

Dust-free sanding is on the rise in the Canadian market, according to Jay Hayward, territory manager with Norton Automotive, a division of Saint-Gobain Abrasives. “I would estimate less than 10% of bodyshops were using vacuum for sanding a couple of years ago. Now, I have six or seven new accounts that have gone in that direction. It’s definitely the way to go.”

Aside from the obvious benefit of reducing contamination in the shop, capturing the dust at the sander gives the technician a better view of the work surface and keeps the abrasive grain exposed for more even sanding.

Norton’s Multi-Air line of abrasives can be used either with a central vacuum system or with self-generating sanders. Self-generating sanders create a vacuum by causing a venturi effect. “Self-generating units allow shops to get into the dust-free scenario for only a few hundred dollars,” notes Hayward. Norton’s Multi-Air discs have 181 small holes to draw away the dust, instead of the six holes that had been traditional for dust-free discs.

Likewise, 3M’s Purple Clean Sanding Discs have 282 holes, in a logarithmic spiral pattern, to give dust a better escape route. The new discs use premium grade abrasives that give consistent performance.

According to 3M, the Purple Clean Sanding Discs last up to two times longer than no-hole abrasives, and have better dust extraction than five-hole and six-hole discs.

“The more we can go into dust-free sanding, the better,” says Ford.

Paper and Tape Must Resist Wind and Water

The high-velocity air movement favoured for drying waterborne basecoat presents two challenges: wind and water. Blowers and fans are prevalent in spray booths adapted for waterborne, so Rob Blue, an account executive with 3M Automotive Aftermarket Division, reminds preppers that vehicles must be wrapped tightly.

“You’re not going to have any issues if you’re using top-grade products. You need treated paper to keep water from penetrating. If water penetrates the paper or tape, it can lift them.”

For the waterborne environment, FBS Distributions offers K-Auto Mask tape, a lowcreped masking tape that provides a thin, sharp edge and a heat-resistant, rubber-based adhesive.

With waterborne basecoat soon to be the required technology for Canadian shops, preppers will need to adjust quickly to its more demanding standards, and adapt their tools and equipment accordingly.

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