The authoritative public forum
  for Metal Finishing since 1989
  

  -----

Paint is bleeding under our masking

February 12, 2009

Hello,

I have a question about masking.
We have been making parts for paint for some time and have really never had a problem.
I'm talking about aluminum and stainless. We have recently gotten a new project that requires a very small edge to be masked. we are having a problem with paint getting underneath the tape.
I was wondering if anyone knew of a putty or a liquid that I could use that would not a problem in 120 degrees for an hour or so.
This particular part has a lube that has been baked on. That is what we are masking off, so the putty or film cannot take the lube off.

Thank-you,

Micheline Forth
finishing company - Savannah, Georgia

---

February 13, 2009

You might try other brands of tape such as ones that have a better glue or possibly a thinner or thicker tape. If vinyl is not working, consider aluminum with a thick glue or even lead foil tape.

You might need to burnish the tape edges with a tongue depressor or thin plastic. You might be able to use a small pizza roller to press the tape onto the metal better. I have heard of a moderately hard silicon roller for that purpose also.

I think that you will find that painted on maskants will be a serious pain.

James Watts
- Navarre, Florida

---

First of two simultaneous responses --

Have you tried silicone masking plugs and tapes? Just type "silicone plugs" into www.

Terry Hickling
Birmingham, United Kingdom
February 16, 2009

---

Second of two simultaneous responses --

I tend to agree with James about using tape. He gives some good suggestions too. The thing to remember about most masking tapes is that they have pressure sensitive adhesives. So what James said about using something to push the tape down is important.

The other thing to keep in mind, is that most adhesives like that also "flow" over time, into the microscopic crevices in the part. You have to push down hard for that to happen properly. So after 4 hours or 6 hours or, ideally, 24 hours, you will have FAR better adhesion than if you lightly tape the part and coat it right away.

I'm not sure about that "baked on lubricant" that you mentioned, too - I wonder if that's what's causing the problems. Though I'm also surprised that the paint will even adhere over that. Is it possible that the temperature at which you're baking the parts softens the lubricant, causing problems with the masking line?

Crepe masking tape, vinyl tape, green polyester tape, aluminum foil tape, lead foil tape - any of those would be good options to try, and are listed in order from lowest to highest cost. Hope that helps.

David Fuller
- Monee, Illinois
February 17, 2009

---

February 23, 2009

Thank-you so very much for the responses.
There seems to be some good ideas.
Finding a tool to promote better adhesion and waiting 24 hrs before paint sounds good. Also aluminum tape might be a good idea.

Sincerely,

Micheline Forth
finishing company - Savannah, Georgia