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Bridge Paint Mishap Ends Fair & Square

Tuesday, September 4, 2012

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When you’re painting 55,000 little squares in 30 colors along a busy, four-lane bridge over the Rio Grande, you might expect some complications.

You just don’t necessarily expect them in that big beige swath in the middle.

 The 55,000 colored squares went great. The big patch of tan epoxy was another story.

 Bob’s Painting (left); City of Albuquerque (right)

The 55,000 colored squares went great. The big patch of tan epoxy was another story.

But that’s where Albuquerque’s year-old $112,000 painting job failed.

Making it right—which everyone has—took a little doing. But persistence and collaboration pay off, especially when bad things happen to good coatings.

Public Art Challenge

The problem involved the city’s famed Montaño Bridge, built in 1997, which for 14 years has sported an 800-yard-long mural by Albuquerque artist Dave Dekker as part of the city’s renowned public arts program.

Bob’s Painting Inc., a prominent local painting contractor, was originally selected to work with Dekker to bring the mural to life on what was then a two-lane bridge with no vehicular traffic.

The art-deco-type design features tens of thousands of neatly arrayed red, blue and green squares that taper off into a sporadic sprinkling on a solid tan background.

Bob’s, which boasts “there is nothing we cannot paint,” recreated the work on the bridge using two-part automotive paint, including metallic hues.

Facelift Plans

Fast-forward to the summer of 2011, when the mural on the bridge—now four lanes and carrying heavy daily motor traffic—was finally set to get a much-needed facelift. Every square would be repainted and a clear sealer sprayed over all.
 
Again, the city turned to Bob’s, which still had all of the original patterns and color records, said Sherri Brueggeman, who heads the Public Arts Program.

 After more than a decade, traffic and time had taken a toll on the mural.

 Bob’s Painting

After more than a decade, traffic and time had taken a toll on the mural.

Bob’s, in turn, also had the same paint supplier, Bond Paint Co., a veteran local company.

The city, contractor and supplier all worked together to revive the mural, using as many of the original materials as possible and triple-checking data sheets for new formulations. Automotive paint was again used for the colors and a tan epoxy for the background.

Something went wrong anyway.

‘Flaking Off, Almost in Sheets’

A few months after the mural was repainted, the clear coat began to peel and disintegrate. Flakes of coating were flying off the bridge as traffic whizzed past.

“The clear coat they had put on was not sticking to the color coat, and it was really flaking off, almost in sheets,” said Brueggeman.

Bob’s, which had guaranteed the job for 10 years, was also perplexed, said Chris Herman, who oversaw the project for the painting company.

Putting their heads together, the painter and supplier determined that all of the colors were adhering well to the substrate, and that the clear coat was adhering to the automotive paint.

It was the clear coat over the epoxy where things fell apart.

Although the product was approved for application over epoxy, “it just didn’t work out,” said Herman.

What Went Wrong…

After considerable testing, Bob's and Bond agreed on a new two-part urethane to clear-coat the epoxy. Bond replaced the material and even chipped in toward the labor for the redo, said Herman.

Bob’s then pressure-washed the failed sealer, cleaned every square inch with a denatured alcohol, and brushed and rolled out the new coat.

It took a crew of eight painters four weekend days to do the work.

…And What Went Right

The new coating is holding well, and city officials are thrilled with the contractor's and supplier’s responsiveness to the problem.

 Two-part automotive paint in 30 colors was used for the squares.

 City of Albuquerque / Flickr

Two-part automotive paint in 30 colors was used for the squares.

All good--but what went wrong? No one is quite sure. Theories include a batch error or a formulation tweak that withered the coating in the brutal New Mexico summer sun.

“The epoxy got chalky from the sun and made the sealer pop off of it,” Herman thinks.

But he adds: “They honestly still don’t know what happened.”

   

Tagged categories: Automotive coatings; Bridges; Coating failure; Contractors; Delamination; Epoxy; Painters; Peeling; Sealers

Comment from John Fauth, (9/5/2012, 9:32 AM)

I'm not sure most people would want their car painted with paints intended for use on concrete. So why would professionals coat concrete with paints intended for use on automobiles? Would anyone suggest painting a metal bridge structure with a concrete coating?


Comment from Tom Schwerdt, (9/5/2012, 10:51 AM)

Clearcoats over epoxy are an iffy proposition. If you have enough UV inhibitor (likely HALS) it will work for awhile. Often enough UV penetrates to degrade the epoxy (chalking.) The clearcoat is then only attached to chalked epoxy and peels. The automotive industry saw this as widespread failures just like this in the 1980's to early 1990s. Remember all the cars with peeling/faded hoods and roofs?


Comment from James Johnson, (9/5/2012, 11:27 AM)

I could see two reasons for using automotive paint. It offers a much wider choice of stable colors and its high performance characteristics. I have often wondered why automotive paint performs so much better than the usual industrial coating. Consider an automotive coating is applied at about 2 mils, stays bonded to a thin substrate, which bends and flexs constantly as it travels down the road at high speed, often impacted by dust and grit at those high speeds and lasts about 20 years or more. Industrial coatings are applied several times as thick to a fairly ridged substrate that sits still, does not flex nearly as much, is not subjected to the same impact, and only occasionally lasts 20 years. The auto industry is also far ahead in corrosion control. Cars are subjected to the same weather and salt conditions as bridges, yet suffer far less corrosion problems, even though it is a more severe service with moving and flexing, yet a much thinner coating. Rust on bridges is still common while rusted vehicles are almost a thing of the past.


Comment from Mike McCloud, (9/6/2012, 8:06 AM)

Great points James. Also, cars are not sandblasted.


Comment from Brian Chapman, (9/6/2012, 8:15 AM)

I agree with James here. Automotive paints are HIGH performance. As long as the proper primer was used the should be no issues with the auto paint on concrete. Todays automotive paints are working on steel. plastic. fiberglass, rubber and many other compounds all on the same vehicle. We paint color bands on large (30 ft +) tournament fishing boats and use all automotive products because of the high-performance. The big draw-back to using automotive finishes is the price. This is a classic case of "you get what you pay for". They cost more because they work better.


Comment from John Fauth, (9/6/2012, 9:08 AM)

How much moisture is moving through those automobiles and their coatings? What are their MVTR's?


Comment from John Fauth, (9/6/2012, 9:38 AM)

In fact, what's the alkalinity of those automobiles? Concrete has a pH level of 12 to 13. I don't know for certain, but imagine those high performance automobile paints might not like that environment.


Comment from James Johnson, (9/7/2012, 10:40 AM)

John - My previous comments about automotive paint versus bridge paint was in regards to steel bridges. I should have clarified that. As Mike pointed out, automotive surfaces are not even abrasive blasted. Automotive paint may be pricey, but I think the industrial coating industry could learn a lot from the automotive industry and the technological advances they have developed, some of which may be adaptable to industrial applications.


Comment from shane hirvi, (9/7/2012, 11:30 AM)

John--the ph of new concrete is 12-13 but as the surface of concrete, through a process called carbonation, reacts with the carbon dioxide in the air the ph reduces to the mid 8 range. However, when you have an active water source moving in the concrete, you wouldn't get this with concrete traffic barriers, alkalies and hydroxides will be deposited on the surface of the slab altering the ph.


Comment from John Fauth, (9/10/2012, 8:28 AM)

James, I agree regarding steel bridge structures. My comments were related to the specifics of the article, which was a concrete structure.


Comment from John Fauth, (9/10/2012, 8:33 AM)

Shane, aren't concrete coatings intended (amongst other things) to prevent carbonation? I'm not sure it's fair to establish the pH level of uncoated, weathered, carbonated concrete as the baseline in order to determine whether a particular coating is advisable in that environment.


Comment from shane hirvi, (9/12/2012, 10:35 AM)

John, people coat/line concrete for a variety of reasons--people coat concrete traffic barriers with silly little blocks of color because somewhere there is a silly person who thinks such silly things are pleasing to the senses. The silly people who come up with these ideas often times fail to look at the mid to long range viability of such things. As far as the ph is concerned, on concrete traffic barriers, it is pretty stable because it cannot be influenced by a live water source. But don't take my word on the matter ph strips are pretty cheap and there are traffic barriers all over the place--I'm sure you won't find that harsh of environments vis-a-vis high ph levels.


Comment from John Fauth, (9/13/2012, 9:50 AM)

Shane, I'm with you about some of the strange things people will do, for any number of reasons. And they rarely consider the outcome of their actions beyond sating some short term need. But I'm confused about where you stand on concrete pH. In your first post, you seemed to imply that the pH will decrease rather readily. Now you're saying it won't? I'm thinking that would come as a surprise to state DOT's that require use of waterproofing admixturs, waterproofing treatments, and a variety of protective coatings on their concrete traffic barriers. Maybe they can afford a few of those pH stips too?


Comment from John Fauth, (9/13/2012, 9:54 AM)

It's also worth mentioning that in many northern climates those concrete traffic barriers are exposed to freeze/thaw cycles and deicing chemicals. In other areas they are exposed to salt water environments. And in most areas it rains. Lowered pH is associated with corrosion of the underlying rebar, and premature deterioration of those concrete traffic barriers.


Comment from shane hirvi, (9/13/2012, 2:59 PM)

John, you said 12-13 I was merely pointing out that 12-13 isn't as common as you believe it to be--like I said ph strips aren't expensive check it out for yourself, don't take my word for it.


Comment from shane hirvi, (9/13/2012, 3:11 PM)

It's also worth mentioning that I've been checking ph of concrete substrates from Alaska to Texas and many states and provences in between over many years. If you are expecting concrete to have a ph in the 12-13 range you will be as confused as I was the first time I actually tested the ph of the concrete I was working on. I went through 20+ strips and a liter of water. Oh and I can also provider photographs and videos of ten or so large concrete coating projects that my company has been working on over the years. Anyhow cheers have a good day and all of that.


Comment from John Fauth, (9/13/2012, 3:55 PM)

Shane, is it possible that we're arguing both sides of the same coin? I'm simply saying that a good concrete coating will intentionally retain a high pH, as a means of protecting underlying rebar. I'm not sure that's really controversial. If you're saying that the pH level of unprotected concrete readily declines, that's not controversial either. Yeah, there's plenty of unprotected, aged concrete out there with substantially lower pH. What's the point?


Comment from Tom Schwerdt, (9/14/2012, 8:31 AM)

Coring the concrete and measuring pH versus depth is a good way to check carbonation and see how much protection your rebar still has.


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