Not logged inAmerican Welding Society Forum
Forum AWS Website Help Search Login
Up Topic Welding Industry / General Welding Discussion / Wheelabrator blasting question for the paint guys....
- - By jwright650 (*****) Date 04-23-2009 15:42
Need some help here. I have a paint spec that requires a sharp angular profile of a given depth. Ok, maybe a couple of questions...LOL

Is there a visual comparator that I should use to make sure that I have enough sharpness?

How do you determine at what point you have crossed over from a smooth, rounded profile into a sharp, angular profile?

I'm using a steel shot and will be adding some steel grit to the mix and just want to get this right the first time around.
Parent - - By hogan (****) Date 04-23-2009 16:20
I have never used one of these but I believe this is what you are looking for.

http://www.ktagage.com/level3.asp?product_ID=25

Good luck getting it the first time. Is this the first attempt at getting profile with a wheelabrator?
Some of that stuff is very aggressive.
Parent - By jwright650 (*****) Date 04-23-2009 16:34
I have that 5x magnifyer(Plus a stronger 20X) and use the textape replica tape...I'm getting the "depth" of the profile just fine, it is just the spec requires a sharp angular profile and ours is rounded from using round shot, so we're adding grit to the mix to gain the sharper profile.

My question is......how do you know when you are sharp enough to call it a sharp, angular profile?
Parent - By jwright650 (*****) Date 04-23-2009 16:38
I should add that I have an outside inspector here who is watching over this job also, and both of us are trying to figure this out so we do it properly. We are in agreement that what we currently have is very rounded, so our company has purchased some grit that should be delivered today sometime, and we will be adding it to the mix...therefore that's where my questions come into play.
Parent - - By CHGuilford (****) Date 04-23-2009 16:42
"Sharp, Angular" are relative terms.  Usually all you need to do is add the grit - as you mentioned - and that will "sharpen" your profile enough to be satisfactory.

There are visual comparators that can be used but I don't have my NACE information handy.  Check with KTA Tator if you want more info on those. 
But I wouldn't go that route if you don't have to.  Usually, most customers are satisfied with looking at the profiles with the naked eye.  Some even run their fingers over the surface to feel the difference (skin oils can cause adhesion problems but it's hard to make them understand that.)

PS - the link hogan provided is exactly what I was talking about but again, don't go there if you don't have to.
Parent - - By jwright650 (*****) Date 04-23-2009 17:15
"Sharp, Angular" are relative terms.-quote

That is exactly what I was afraid of.....I wish it was more black and white with some of this stuff...LOL

I will keep adding grit until these guys are satisfied that it is sharp enough to be called sharp.

To be perfectly honest, this is the first time that we have ran across this in all of these years, but then again this is the first time we were forced to use a different paint mfg that we have never used before. The job specs called for our normal Tnemec paint system, but someone else (another fabricator) messed up and used this other paint system on a different portion of this project, now the architech is demanding that we follow suit since the other fabricator's steel is already erected....uggh.
Parent - - By kipman (***) Date 04-23-2009 19:57
John,
Wait until you try to determine a white as opposed to a near white blast.  Then you'll see relative/subjective.
Parent - - By jwright650 (*****) Date 04-23-2009 20:49
Best cleaning that we've had to meet with this equipment was an SP10...haven't had to try for the SP5 yet.....however, if you start with a really clean Grade "A" piece I expect you can get a white blast with 0% staining.....
Parent - - By dbigkahunna (****) Date 04-23-2009 23:03
[deleted]
Parent - - By jwright650 (*****) Date 04-24-2009 11:03
Thanks for the reply.....I contacted the paint mfg yesterday and they are not budging on this, they are mandating that we have the sharp angular profile due to they warranty that they are providing on their product. Normally they said the rounded shot profile is good enough, but the owner of this project has asked for an extended warranty, so they aren't budging from the paint spec/product data sheet in this case. This is a zinc rich primer that requires this profile, I suppose it's due to the amount of solids in the mixture.
Parent - - By dbigkahunna (****) Date 04-25-2009 01:32
[deleted]
Parent - - By jwright650 (*****) Date 04-25-2009 17:51
2.5-3.5mils
Parent - - By dbigkahunna (****) Date 04-26-2009 00:48
[deleted]
Parent - By Joseph P. Kane (****) Date 04-26-2009 15:23
A 3 to 5 Mil profile will take a lot of paint layers to assure full coverage!

Most profiles that I have run into require 1 to 3 mils. 

Remember, paint thickness over a given blast profile is not just a simple addition problem.

Most paint systems cannot work after a certain dry film thickness.  Even sophisticated multi-layer systems have individual layer and cumulative layer limits!
Parent - By jwright650 (*****) Date 04-23-2009 17:25
As for that G/S comparator....(for grit shot mix)...I have that and use it along with the testex tape to verify that I have the correct profile depth...but this sharp and angular term has thrown a monkey wrench in the works.
Parent - - By FixaLinc (****) Date 04-24-2009 06:33
Yep sounds like a trick question to me.  Maybe steel grit ?  Maybe ask someone at USF Surface Preparation that's who I checked with to get the finer glass beads I needed for aluminum and those 80 grit were way too sharp to my liking. 

http://www.surfacepreparation.com/steel-grit.html

http://www.surfacepreparation.com/
Parent - - By jwright650 (*****) Date 04-24-2009 11:06
Yes, we have a sheel shot in the machine and are adding a steel grit of the same BN hardness as the steel shot. From what I understand, this steel grit is is nothing more than steel shot that has been mashed up into jagged pieces.
Parent - - By jwright650 (*****) Date 04-24-2009 13:55
Whelp, the first piece just came out of the blast and we checked the profile and got 3.5mils with a considerably sharper profile...inspector is happy, so we're rollin' on with it. Thanks to all who responded.
Parent - - By CHGuilford (****) Date 04-24-2009 16:27
Just so you know, you can sharp angular and a lesser profile with finer grit.  We have had jobs that require a 2.0 mil Max profile and was able to get it.

Higher profiles mean you'll use more paint but watch out the you are not exceeding the manuf. recommendations.
Parent - By jwright650 (*****) Date 04-24-2009 17:59
Thanks Chet for the word of caution about overages in paint use...I was aware of that, but we are within tolerance this time, so life is good. We set up our DFT gage on the blasted steel, so like you stated, if the profile was too deep, we would be just wasting paint trying to get the mils of paint above those peaks. Thanks for the reminders guys....
Parent - - By Mikeqc1 (****) Date 04-24-2009 17:21
I have Run accross this many times, the forum has hit it right on the head for you.
The angular profile is what is needed, as ive seen plenty of profile depth yet when performing an adhesion test the paint poped right off.
When in doubt i always run a test plate and do a pull test.
MDK
Parent - - By jwright650 (*****) Date 04-24-2009 18:03
I may purchase a pull off/adhesion tester if it looks like we might get into these jobs with very particular specs. This job is a once in a blue moon job for us, so I'll be glad to see this one go...the handling/drying time is killing our shop. Standing around watching paint dry for 10 hours at a stretch is not very fun, then factor in 3 coats...uggh.
Parent - - By Mikeqc1 (****) Date 04-24-2009 18:22
DEPENDING ON HUMIDITY AND TEMPS ....DRYING TIME COULD BE ACCELERATED .
Parent - By jwright650 (*****) Date 04-24-2009 20:22
Those parameters are why the drying time is what it is.....been cool and humid. But it's climbing today up towards 80°...so that will help speed things up
Parent - - By FixaLinc (****) Date 04-24-2009 20:17
Yeah that's what it is just sharper.  I got crushed glass once it was just sharper and more jagged than glass beads that had rounder profile.  Good luck with the paint now. 
Parent - - By TozziWelding (**) Date 04-25-2009 23:15
These guys will help with anything paint and have great products http://www.carboline.com/
Parent - - By eekpod (****) Date 04-27-2009 16:42
John, Be careful that you don't end up with a surface that is too rough or else you may develope pinpoint rusting due to the fact that the difference between the depth of the valley and the height of the peak can be more than needed if the surface is overblasted.  My understanding is that the mils is the average of this height.  Also it depends on the size grit you are using.
Getting back to the angular issue, it could be considered the angle that the blast media is applied from.  Where is you hand sand blast something you would never hold the nozzle 90 degrees to the surface, you would angle it so it blows away from the operator, that would make an angular profile for the paint to adhere to.  Hope this doesn't mess you up.
Parent - By jwright650 (*****) Date 04-28-2009 11:15
Hi Chris,
All is good with the profile now, we learned something, so this should make us better as a company and help us keep our eyes on those paint specs a little closer. As for the media hitting @ 90° to the surface, our wheelabrator has wheels that are spaced so that the media is striking at an angle so that isn't an issue. All was good, as Chet and others had said, by just adding the grit to the mix.

Actually, having a really good paint inspector here has really been a big help in that I can get my guys to just follow along and stick to the basics of prepping and painting, and monitoring what we are doing so that it doesn't go way wrong. This guy(inspector) has helped my guys in more ways than he or they even realize...LOL

Thanks for your input.
Up Topic Welding Industry / General Welding Discussion / Wheelabrator blasting question for the paint guys....

Powered by mwForum 2.29.2 © 1999-2013 Markus Wichitill