Shop Coat Versus Field Coat: the Pros and Cons

From JPCL, September 2016

By Charles S. Brown, Greenman-Pedersen, Inc.

There seems to be a trend for bridge owners to believe that applying all three coats of paint in the shop is more cost-effective and will provide a better coating job on new steel. In this article, the author compares and contrasts shop coating and field painting on new steel and the various cost differences through two case histories from the Maryland State Highway Administration....


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Tagged categories: Bridges; Coating Application; Cost-savings; Roads/Highways; Shop-applied coatings; Site/field testing

Comment from David Grove, (10/25/2016, 6:58 AM)

I can envision that several factors can change the impacts/costs. Have you assessed the following scenario? Blasting and priming the steel, masking the faying surfaces (after the IOZ primer, then applying an epoxy with an extended recoat ensures that the best conditions can exist for the main structure of the coating system. The field would need to touch up any primer damage then apply the second coat over only where required. Of course, a full topcoat would be required in the field. This takes advantage of the unlimited recoat value of IOZ (not forgetting to inspect for zinc salts and contamination), and the extended recoat window of the epoxy. The field applied topcoat provides the appearance the public would want to see. I can see that by utilizing the extended recoat windows of the primer and intermediate coatings, the costs may be slightly less, but the possibility of a longer lifespan, the overall costs would decrease over time.


Comment from trevor neale, (10/25/2016, 3:58 PM)

The photo was bad example, looks like rivets to me - not sure shop painting was ever considered for them.


Comment from Eric Williams, (10/27/2016, 10:34 AM)

Charles has done a great job on this article. As a Bridge Fabricator I have seen that State DOTs, and Municipalities have different philosophies about how they want the Bridge to arrive in the field. For the Fabricator it is much more efficient to blast and apply IOZ. This translates to quicker turn around and shop through put. Even when a zinc, epoxy, urethane system is required in the shop the faying surfaces are always completed with intermediate and finish in the field.


Comment from Rudy Hudale, (12/9/2016, 9:10 AM)

Phenomenal Photos!!!!! Very well explained!!!!! The only thing I disagree with is the last 6 bullet points and the only reason is because, NUMBER 1 on that list should be surface preparation. That is the number one cause of coatings and lining failures.


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