What did I do to deserve this/What went wrong?

Rizmoine
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Re: What did I do to deserve this/What went wrong?

Post by Rizmoine » Thu Feb 06, 2020 8:01 pm

It is a textured paint we do check thin knees with an electronic gage.

This issue I quit new. We coated a lot last week without any issue. I suspected air humidity. We change the filters of our devilbis air dryer. Should I suspect the hose?

Rizmoine
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Re: What did I do to deserve this/What went wrong?

Post by Rizmoine » Thu Feb 06, 2020 8:05 pm

We have a three stage cleaning process. Sand, soap cleaning, phosphate, rince and drying before coating. We are painting steel.

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hjeades
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Re: What did I do to deserve this/What went wrong?

Post by hjeades » Fri Feb 07, 2020 8:28 am

Rizmoine wrote:
Thu Feb 06, 2020 8:05 pm
We have a three stage cleaning process. Sand, soap cleaning, phosphate, rince and drying before coating. We are painting steel.
Mil scale can have oils under it in a way. Steel is best if its blasted clean. If its oily steel clean first then blast.
You can outgas the parts firts as well once cooled then coat. If you dont have a way to blast them then definitely outgas the parts first.

Is your air filter a desiccant dryer? Air compressors will put out air with oil in it from the compressor pump
itself as a norm. Its not heavy with oil but does have it. After a time oil builds up in the air lines and can cause
contamination on the parts. You can check you air for heavy oils by blowing air into a clean towel to see if it collects any oil on it. Moisture in your air lines can carry oil as well and the two together can wreck havoc from time to time
on parts. Constantly drian water from your compressor. A good desiccant dryer will stop both. If you do have one make sure the desiccant is good thats in it. If the desiccant looks yellowish thats the oil its cleaning from your air.

My best guess is oils on the parts. Some storage oils are difficult to git rid of out gassing is best.
Hope this helps
Harley
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Rizmoine
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Re: What did I do to deserve this/What went wrong?

Post by Rizmoine » Fri Feb 07, 2020 8:47 am

Thank you. We have a devilbis unit. One section has marbles and two others has filters. We change marbles and filters once every 3 months or when the marble color indicator is white/yellow.

About out gassing, how long and how out should we bake to make sure it is out gassed?

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hjeades
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Re: What did I do to deserve this/What went wrong?

Post by hjeades » Fri Feb 07, 2020 9:00 am

Rizmoine wrote:
Fri Feb 07, 2020 8:47 am
Thank you. We have a devilbis unit. One section has marbles and two others has filters. We change marbles and filters once every 3 months or when the marble color indicator is white/yellow.

About out gassing, how long and how out should we bake to make sure it is out gassed?
Next time you change the desiccant (marbles) check it to see if its capturing oil from your air. This will help
you to know whats going on with your air.
Harley
Happiness is crusing in your street machine with a big breasted woman and a cold beer!
Definition of a Street Machine: A high horse power vehicle able to burn tires in high gear, & capable of evading high speed pursuit.
Restoration is not just a way of life, it's a way to bring new life. Save a car build a hot rod!
http://www.likenewparts.com" onclick="window.open(this.href);return false;

Knick
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Re: What did I do to deserve this/What went wrong?

Post by Knick » Fri Nov 13, 2020 10:14 am

Hey guys

I have one for you to look at and give your thoughts.

I have a piece that keeps bubbling when trying to cure it.
Here are the steps I have taken.

Blast with new media.
wipe with acetone.
Coated fine then put in oven and small bubbles all over.
blast again, (no wipe down) put in oven, to out gas it for maybe 15mins at 400.
Tried again same thing.

Blast a third time and bake at 550 for 30 mins and try again. (no wipe down)
put in oven with color on it (2 stage color needs clear) baked for about 2-3 mins after flow out and got the same thing.


I am pretty sure its a out gassing problem, but not sure how to fix it. Any help would be appreciated.
The part is some kind of a casting. Maybe cast iron but its not magnetic so I don't know (part of a outdoor light) it is heavy for its size.
I have lots of parts from these lights and this is the only one that gave me problems and I had 6 of these parts
exactly the same but only one bubbled.

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hjeades
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Re: What did I do to deserve this/What went wrong?

Post by hjeades » Fri Nov 13, 2020 11:34 am

Some cast pieces outgas bad a lot but there are steps you can do to coupe with it. First after it cools
sand those spots to insure its a outgas issue plus it will smooth the area so you're not seeing the same
spots again. Look real close at the spots as you sand them, are they hollow bumps? Or is there dirt you're
sanding out? I'm sure its outgas but better safe than sorry. Also make sure you finish sand with a fine sandpaper so the sanding doesnt leave small fibers standing up which will look like dirt in the color.

Okay assuming we now know its an outgas issue you can use a primer to stop outgassing which is shot when the part is hot at the primers coating temp thats listed in the instructions for it. The primer will also offer more protection for your customers piece especially if its an outdoor piece. Or you can just coat the color you are doing when the part is at temp which is called hot flocking. When you do either of those you have to move quickly from the oven to the booth and shot the powder. Two big cautions when doing this. "One" you can get burnt handling the part as it will be at cure temp for the color you are shooting so be smart be careful. "Two" it is real easy to over coat and end up with runs and/or sags in the powder. When hot flocking adjust your gun down so it coats slower than normal this will help with the coating. Once the piece is coated straight back in the oven. Keep in mind its still "hot" so you can get burnt still and everything in the air will stick to it now.
Hope this helps.
Harley
Happiness is crusing in your street machine with a big breasted woman and a cold beer!
Definition of a Street Machine: A high horse power vehicle able to burn tires in high gear, & capable of evading high speed pursuit.
Restoration is not just a way of life, it's a way to bring new life. Save a car build a hot rod!
http://www.likenewparts.com" onclick="window.open(this.href);return false;

Knick
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Re: What did I do to deserve this/What went wrong?

Post by Knick » Sat Nov 21, 2020 9:07 am

Thank you for the tips. I did not see this till after I was done. I ended up blasting the part again and out gassed it at 550 for about 60 mins. I then coated it again and it was much better but still looked to have some spots in it.
I come from a liquid painting background so I am sure it was not dirt.

I did several of theses castings and this one was the only one I had problems with.

It seems like the part just continued to outgas no matter how many times I heated it. Is this what you have found?

I had already finished this when I saw your post. If I run into this again I will try your tips above or maybe I will just stay away from cast parts. :lol:

Thanks again!

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hjeades
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Re: What did I do to deserve this/What went wrong?

Post by hjeades » Sat Nov 21, 2020 9:43 am

Sometimes yes thats what you will find with cast parts. Not always though. Sometimes it has to do with
how porus the metal is and/or how much as well as what kind of oils were used it the process of making
the cast piece. As time goes by you will see some ols will burn off and become a stain or burn away completely
while others will just get hot and flow around. A lot of greases will do that as well. Good luck and welcome
to the madness
Harley
Happiness is crusing in your street machine with a big breasted woman and a cold beer!
Definition of a Street Machine: A high horse power vehicle able to burn tires in high gear, & capable of evading high speed pursuit.
Restoration is not just a way of life, it's a way to bring new life. Save a car build a hot rod!
http://www.likenewparts.com" onclick="window.open(this.href);return false;

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