Problem W/ Polyurethane Top Coat Over Spray Paint - Painting - DIY Chatroom Home Improvement Forum


Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > Painting

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Reply
 
Thread Tools Display Modes
Old 03-23-2012, 09:15 PM   #1
Newbie
 
Join Date: Mar 2012
Posts: 2
Rewards Points: 10
Question

Problem w/ polyurethane top coat over spray paint


I am painting a shot put, as in a 6-lb iron ball for track-and-field.

I sanded off what was left of the old finish. I put on a coat of Rustoleum metal primer (spray). I put on a few coats of oil-based Rustoleum paint (spray).

The problem is the protective coating over the paint. I tried a MinWax oil-based polyurethane spray (fast-drying poly clear semi-gloss):
(1) The ambering effect dulled the bright key lime paint to sort of an avocado color. In hindsight, the label warns of this.

(2) After 24 hours, the polyurethane was tacky/gummy. I could rub it off with my thumb.

So my question is whether I need to do something different (wet sand the under coat, wet sand the poly, let it cure longer, etc.) or if I should use a different coating altogether.

A shot put takes a lot of abuse dirt, sand, mud, grass. I anticipate that I will have to repaint it every spring, and thats fine, but Id like to get a couple months out of the paint job. (The factory powder coating was completely worn away down to bare metal after one season.)

Ideally, I would like a coating that is (a) tough enough to take some abuse (b) without muting the bright color. However, the toughness is more important than the color. [Lime green was the athlete's idea. I couldn't talk her out of it.] :-)

Advertisement

pablopaul is offline   Reply With Quote
Old 03-23-2012, 10:28 PM   #2
Member
 
Join Date: Nov 2011
Location: Hartfield VA
Posts: 27,732
Rewards Points: 580
Default

Problem w/ polyurethane top coat over spray paint


Powder coating is one of the longest lasting finishes you can have, it will long out live a painted finish on metal.
Poly should never have been added over the paint.
If your going to use paint then your going to have to deal with having to redo it after a few uses.

Advertisement

joecaption is online now   Reply With Quote
Old 03-23-2012, 11:58 PM   #3
Newbie
 
Join Date: Mar 2012
Posts: 2
Rewards Points: 10
Smile

Problem w/ polyurethane top coat over spray paint


Thanks for the feedback, Joecaption. As you can imagine, there isn't much out there when you Google "How to paint a shot put." So I was going with what little direction I could find.

I will look into powder coating when the paint wears off (which shouldn't be long). I wasn't impressed with the factory coating on the shot put because it wore off so quickly and completely, so I was thinking there might be some sort of poly/varnish/lacquer that would absorb the abuse.
pablopaul is offline   Reply With Quote
Old 03-24-2012, 06:00 AM   #4
paper hanger and painter
 
chrisn's Avatar
 
Join Date: Dec 2007
Location: Hagerstown MD
Posts: 6,855
Rewards Points: 2,218
Default

Problem w/ polyurethane top coat over spray paint


[quote=pablopaul;884193]Thanks for the feedback, Joecaption. As you can imagine, there isn't much out there when you Google "How to paint a shot put." So I was going with what little direction I could find.

I will look into powder coating when the paint wears off (which shouldn't be long). I wasn't impressed with the factory coating on the shot put because it wore off so quickly and completely, so I was thinking there might be some sort of poly/varnish/lacquer that would absorb the abuse.[/quote]



nope
chrisn is offline   Reply With Quote
Old 03-24-2012, 10:47 AM   #5
Member
 
Join Date: Oct 2011
Posts: 432
Rewards Points: 254
Default

Problem w/ polyurethane top coat over spray paint


Quote:
Originally Posted by pablopaul View Post
I am painting a shot put, as in a 6-lb iron ball for track-and-field.

I sanded off what was left of the old finish. I put on a coat of Rustoleum metal primer (spray). I put on a few coats of oil-based Rustoleum paint (spray).

The problem is the protective coating over the paint. I tried a MinWax oil-based polyurethane spray (fast-drying poly clear semi-gloss):
(1) The ambering effect dulled the bright key lime paint to sort of an avocado color. In hindsight, the label warns of this.

(2) After 24 hours, the polyurethane was tacky/gummy. I could rub it off with my thumb.

So my question is whether I need to do something different (wet sand the under coat, wet sand the poly, let it cure longer, etc.) or if I should use a different coating altogether.

A shot put takes a lot of abuse dirt, sand, mud, grass. I anticipate that I will have to repaint it every spring, and thats fine, but Id like to get a couple months out of the paint job. (The factory powder coating was completely worn away down to bare metal after one season.)

Ideally, I would like a coating that is (a) tough enough to take some abuse (b) without muting the bright color. However, the toughness is more important than the color. [Lime green was the athlete's idea. I couldn't talk her out of it.] :-)
Painting a shot put, eh? Not the most common discussion we've had on this forum, but I s'pose it can be done. First off, Powder Coating may have a few advantages to liquid paint, but let's not assign super-performance characteristics to a very limited application process...from a resins perspective, they are pretty much the same as liquid paints (alkyds, vinyls, epoxies, etc.), and each comes with their own inherent advantages and dis-advantages.

...and if it were relevant to this particular thread, I'd mention that there is absolutely NOTHING wrong with putting a clear poly over a painted finish.

Your problem is the surface to be painted, and the exposure and abuse the painted item must endure. First, the steel that makes up your shot put is hard, slick and impervious. Unfortunately, this does not make an ideal surface for conventional coatings. Second, the exposure of hurling a 6 pound steel shot, onto any surface, doesn't really fit the "regular and expected" abuse a typical coating should endure.

So, you're gonna have to think more in terms of non-conventional coatings... which is no real big deal, except you're only gonna need a brushful of product to coat this thing a couple times over. These high performance, non-conventional coatings are usually found in no less than gallon quantities and often times are 2 component (parts A & B to be mixed at time of application).

A kick-a$$, bulletproof system would involve (a) Etch the shot put with acid to create a profile necessary for good mechanical adhesion...(b) prime with a high build poly-amide cure epoxy...(c) apply 1 coat of a poly amine cure epoxy tinted to Lime Green, and finally (d) apply 1 application of a moisture cure urethane for maximum impact and abrasion resistance.

Now, if you can purchase all these products, you're probably looking in the neighborhood of $200 material to paint this 6# shot put - and some may actually think that's too much effort and money, but it's still most likely to be cheaper than having it re-powdered - or buying your own powder coating gun, and oven, to do it yourself.

...or you could just do it again like you did before, but this time etch the steel first, and realize you're gonna have to touch it up occasionally, or re-do it maybe a couple times per season...or just spray paint it lime green and figure on repainting after every track meet (thats what professional and college football equipment managers do with the players helmets after games).

P.S. - even though I said there's nothing wrong with applying a clear poly over an alkyd coating, you really won't be gaining any advantage to doing so...so don't do it. Good luck.
ric knows paint is offline   Reply With Quote
Old 03-24-2012, 11:05 AM   #6
Doer of Many Things
 
poppameth's Avatar
 
Join Date: Oct 2008
Location: Staunton, VA
Posts: 1,179
Rewards Points: 526
Default

Problem w/ polyurethane top coat over spray paint


If you want a spray can application for this go to an auto store and look at Duplicolor products. use their primer, paint and clear topcoat for a completely compatible system and make sure to follow the instructions. If you want very durable finish take the thing to Line-X and have them spray it with one of their bedliners, which are now available in several colors. I wonder if their lifetime touchup warranty covers shot puts?
__________________
Darkling Designs
poppameth is online now   Reply With Quote
Old 03-24-2012, 05:53 PM   #7
paper hanger and painter
 
chrisn's Avatar
 
Join Date: Dec 2007
Location: Hagerstown MD
Posts: 6,855
Rewards Points: 2,218
Default

Problem w/ polyurethane top coat over spray paint


Quote:
Originally Posted by ric knows paint View Post
Painting a shot put, eh? Not the most common discussion we've had on this forum, but I s'pose it can be done. First off, Powder Coating may have a few advantages to liquid paint, but let's not assign super-performance characteristics to a very limited application process...from a resins perspective, they are pretty much the same as liquid paints (alkyds, vinyls, epoxies, etc.), and each comes with their own inherent advantages and dis-advantages.

...and if it were relevant to this particular thread, I'd mention that there is absolutely NOTHING wrong with putting a clear poly over a painted finish.

Your problem is the surface to be painted, and the exposure and abuse the painted item must endure. First, the steel that makes up your shot put is hard, slick and impervious. Unfortunately, this does not make an ideal surface for conventional coatings. Second, the exposure of hurling a 6 pound steel shot, onto any surface, doesn't really fit the "regular and expected" abuse a typical coating should endure.

So, you're gonna have to think more in terms of non-conventional coatings... which is no real big deal, except you're only gonna need a brushful of product to coat this thing a couple times over. These high performance, non-conventional coatings are usually found in no less than gallon quantities and often times are 2 component (parts A & B to be mixed at time of application).

A kick-a$$, bulletproof system would involve (a) Etch the shot put with acid to create a profile necessary for good mechanical adhesion...(b) prime with a high build poly-amide cure epoxy...(c) apply 1 coat of a poly amine cure epoxy tinted to Lime Green, and finally (d) apply 1 application of a moisture cure urethane for maximum impact and abrasion resistance.

Now, if you can purchase all these products, you're probably looking in the neighborhood of $200 material to paint this 6# shot put - and some may actually think that's too much effort and money, but it's still most likely to be cheaper than having it re-powdered - or buying your own powder coating gun, and oven, to do it yourself.

...or you could just do it again like you did before, but this time etch the steel first, and realize you're gonna have to touch it up occasionally, or re-do it maybe a couple times per season...or just spray paint it lime green and figure on repainting after every track meet (thats what professional and college football equipment managers do with the players helmets after games).

P.S. - even though I said there's nothing wrong with applying a clear poly over an alkyd coating, you really won't be gaining any advantage to doing so...so don't do it. Good luck.

Well, I am glad you added the PS
chrisn is offline   Reply With Quote
Old 03-25-2012, 06:34 AM   #8
Member
 
Join Date: Jan 2011
Location: Cape May, NJ
Posts: 2,392
Rewards Points: 1,000
Default

Problem w/ polyurethane top coat over spray paint


About the PS, IN THIS CASE, the poly won't add anything. Poly does protect painted surfaces from mild usage wear and tear. This is an ongoing issue with Joecaption. I've said it before joe, and I'll say it again, poly is used in faux decorating to seal the finishes and protect them from wear, among other applications in painting for poly over paint. Why do we put poly over stained hardwood, not for the sheen alone?

Advertisement

jsheridan is offline   Reply With Quote
Reply

Tags
painting painting metal , polyurethane top coat , spray polyurethane , wet sanding


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
mixing polyurethane/clear coat sealers into paint?? squiggles Painting 30 11-26-2014 08:13 AM
Cleaning brush StevenH Painting 19 02-06-2011 12:13 AM
semi gloss enamel vs eggshell enamel NoExperience Painting 18 03-05-2009 05:57 AM
Painting a room for new baby. Lots of questions. SuperAkuma Painting 15 01-01-2009 11:18 AM
Paint will not stick in Bathroom! SGTHetland Painting 9 08-18-2008 12:04 AM




Top of Page | View New Posts