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December 18 - December 22, 2017

How do you determine whether a lead-bearing coating can be overcoated or must be removed and replaced?


Selected Answers

From Larry Muzia of Exceletech Coating & Applications, LLC on December 20, 2017:
Suboxide of lead was a wonderfully performing inhibitive pigment, albeit the environmental health issues. I have seen it perform over 30 years over mill scale when used in oil-based systems that had great wetting ability. Lead soaps would over time develop with the film matrix and keep the coating film from cracking by keeping it flexible. In addition, it had very good inhibitive qualities. I agree with the comments above that if the coating is well adhered, overcoating is a suitable alternative.

From Chad Laubenthal of Marathon Pipeline on December 20, 2017:
I agree with the comments regarding coatings that are still tightly adhered. We have had jobs where the lead coating was so tightly adhered it was very difficult to blast off. This raised the question, why remove the coating if it is still good? If the coating is suitable for overcoating, this can be a fraction of the costs compared to full blast and recoat.

From Warren Brand of Chicago Corrosion Group on December 19, 2017:
I agree with all of the comments, though, Erik, I always heard that lead was used because of its incredible ability to resist corrosion and provide a smooth finish. Either way, another overriding issue is a cost-benefit analysis and location. We worked on a very large coal stacker with a lead-based primer. They were getting ready to remove the lead when our firm pointed out that the lead was well adhered and the site was never going to be anything but an industrial site. If the site were in a city park, school, commercial area, even though it may be technically feasible to overcoat the LBP, it may make long-term sense to remove the LBP, and reduce future liability and mitigation.

From Frank Rea of GPI - Greenman Pedersen, Inc. on December 19, 2017:
The decision for full removal and recoat versus overcoating should be made based on the existing coating condition. There is no legal requirement that lead paint must be removed. The first step is to perform an existing coatings condition assessment. Evaluate the type, degree and distribution of the corrosion and other coatings defects (peeling, cracking, etc.); determine the number of coats and thickness of coats; measure the adhesion; and examine the substrate for mill scale. Typically, if the corrosion or defects (peeling, cracking, etc.) are in localized spots on less than 25% of steel surfaces; adhesion is ASTM D 3359, 3A or better; and the existing coatings do not exceed 20 mils thickness, the structure is a candidate for overcoating,which should be less expensive than full removal and repaint.

From Chad Laubenthal of Marathon Pipeline on December 19, 2017:
Specification SSPC-TU 3 (Technology Update NO.3 Overcoating) has guidelines on when a coating is suitable for overcoating.

From Erik Andreassen of CPS on December 18, 2017:
Lead was added to coating primarily to assist the drying of the coating. The U.S. and many parts of the world have banned this material from being added to coatings.For removal, request the assistance of a company licensed to remove, handle and dispose of toxic waste. Do not consider re-coating.

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Tagged categories: Lead; Overcoating lead; Surface Preparation


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