Letter 32053

One part epoxy paint  

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We have over 2000 fire hydrants that we are going to repaint over the next year. We are looking for one part epoxy paint (white) that does not require a primer after sand blasting. It must have a rust prevention, and brush or airless spray application. This paint needs to have a guaranteed life of 5 years or better. Must be waterproof, and resistant to all weather related exposure.

Thanks for your reply

Bill Harris
City of Texas City - Texas City, Texas, USA

Your requirements cannot be met in a true epoxy. An epoxy cures by the chemical reaction between a resin (Part A) and an activator (Part B) There are no one-part epoxies. One-part sprayable epoxies are actually epoxy-alkyds that do not have the corrosion protection or weatherability of chemically-cured (2-Part) epoxies. Another disadvantage with epoxies is that they chalk in outdoor exposure. I believe you would be better served by using a moisture-cured urethane (MCU). MCUs are single component, can be sprayed, brushed or rolled. They develop a hard gloss finish that is very durable and does not chalk. They adhere well to marginally prepared surfaces containing tight rust. Generally complete cleaning and removal of all existing old paint and rust by grit-blasting is not required for painting with MCU's. However the film build (DFT) attainable with an MCU is in the range of 2.5-3.5 mils. I would recommend adding an MCU sealer-primer as the first coat.

E, Bud Senkowski, PE
KTA-Tator, Inc. - Barnegat, NJ

Mr Sendowski's response to the question about 1 Part Epoxies has some truth to it. I agree that in many cases 1 Part Epoxies are basically alkyds, however, this is definately untrue of some 1-Part epoxy. So I am here to tell you, no, not all epoxies are a reaction between an A & B component, have poor weathering properties or chalk . My company produces a wide variety of government spec, industial, commercial and consumer epoxies. Of these 8 - 10 products, three of these come to mind that, although being epoxies, are neither two component (A&B) nor are they alkyds. In fact two of them are water based and single component. Additionally, the paint and coatings industry is chok full of companies, large and small, producing water-based single component epoxy floor coatings so we are not alone.

Thanks,

Peter Harrett
- Marysville, Washington, USA

Pl specify the requirement of Blast cleaning for Epoxy painting on the Steel surfaces.

What should be the degree of cleanliness of metal surfaces i.e. St 2 or St3 will be acceptable for epoxy painting ?

Regards

Negi

Kishan S. Negi
- NEW Delhi, INDIA

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