Powder coating tape tip: Masking large, open areas

It can be expensive to re-coat a part because masking failed - because that masking was tasked with something it wasn't designed to do. 

Here's how to choose the right masking tape product for the job. 

For high temperature masking tapes, that may require using a more expensive tape – but it will do the job right the first time, too. Ultimately, that saves you time, money, and headaches – because it lowers or eliminates the need for costly rework. Just be sure to charge accordingly.

What do we mean by all this?

When a large area needs to be masked off (anything 6” to 8” square or bigger, for example), it can be tempting to think that a large piece of the green polyester masking tape is the best way to mask it. And in some cases, it may be. Here's some options to consider to avoid headaches:

Option 1

 For small quantities or one-off parts: Tape the edges with 1” to 2” tape, while covering the center with paper (that has a flash point is 451F) or aluminum foil (check the cost per square inch/foot first). Not only does this save money in most cases because the paper or aluminum foil costs far less than the tape, it also reduces the possibility of tape-shrinkage. This can "drag" partially cured powder across the edges of a part - not good! The paper and aluminum foil don't tend to do that, and by using less tape, the powder stays where it should. More on the "why" of this below. 

Option 2

The above assumes the area is all one flat surface. And that adds a wrinkle to this - not just figuratively, but it can in actual practice. 

When the area is flat all the way across, the tape heats up at the same rate as the part does, so reaching the part mean temperature (PMT) for powder curing takes longer for the tape – just like the metal part. This is because the tape is literally touching - because it is all-the-way-across adhered to - the part.

But what about something like a valve cover? There’s a narrow, flat surface area around the outside edges, but a larger open area that is covered with tape that is unsupported. In that inner section, the tape doesn’t touch any metal – just air from both sides. Doing the paper/aluminum foil trick with tape around the edge is impractical now.

Then what? Green or blue poly all the way around?

Not quite. That might seem to save money, but the unsupported polyester in the open area heats up quickly, and over time, can shrink – especially if the oven needs to be around 400F, 410F or 425F to get the PMT up faster. As a result, the tape gets hot almost instantly, and that can cause stringy, partially cured powder to get dragged across the flat surface of the valve cover as the inner section shrinks slightly.

That leaves a bit of a mess, and additional time and work. What to do?

Try using a higher temperature rated tape across a large, unsupported surface that will heat up faster than the part. Viadon carries 425F orange polyester tape, and 500F polyimide (amber) tape and glass cloth (white fiberglass) tape that are perfect for these situations.

Other powder coaters do this routinely, because in the long run, they save time – and money – as a result. Because it nearly always eliminates the need for rework - which due to the labor involved, usually costs far more than doing the job right the first time with a bit more expensive tape. 

Got questions about this issue or these tapes? Send us an email or give us a call. We're happy to discuss how to best mask off parts successfully so you can get parts back to your customers done right the first time. 

Viadon. A cut above.