Problem Solving Forum
October 24 - October 30, 2011
What can be done to prevent rust bleed in crevices when applying a zinc/epoxy/urethane system?
Selected Answers
From
Eslope Iwema of TOTAL E & P Nigeria Limitedimited on
October 31, 2011:
The crevices should be suitably dressed open to al ...read more
The crevices should be suitably dressed open to allow stripe coating by brush into the innermost portion of the crevices with the 3-coat system.
From
bryan buckley of corcon inc. on
October 29, 2011:
All of the above -- you must properly stripe coat ...read more
All of the above -- you must properly stripe coat with zinc and epoxy using a brush for these crevices, then apply caulking as needed and then apply finish coat.
From
Mike Beitzel of Modjeski and Masters on
November 1, 2011:
If crevices are filled with unremoved crevice corr ...read more
If crevices are filled with unremoved crevice corrosion or are open after sand blasting, apply a low-viscosity, penetrating epoxy sealer by brush, then a stripe coat by brush of the three-coat system, followed by a topcoat of color-matched silicone caulk to fill any moisture traps.
From
Billy Russell of D&R COATING INSPECTION on
October 25, 2011:
Cut in epoxy with a brush and roller. Add a d ...read more
Cut in epoxy with a brush and roller. Add a detailed epoxy stripe coat of all edges and crevices with a brush and roller. You cannot seal the crevices with a spray gun.
From
jesse chasteen of schriener construction on
October 24, 2011:
Many specifications address this issue with a requ ...read more
Many specifications address this issue with a required application of a compatible caulking prior to applying a finish coat.
From
Larry Muzia of Exceletech LLC on
November 3, 2011:
Obviously, this is a ...read more
Obviously, this is a tough area to properly protect, and although the penetrating epoxy will adhere well if applied at the proper film build and not too excessive, it still is only a very thin film. I agree with the use of a high-quality caulk or possibly a tape wrap product.
From
Thomas Hill of Lyon shipyard on
November 2, 2011: This is an easy fix. Devoe makes a product call ...read more
This is an easy fix. Devoe makes a product called 167 pre prime, a 100% wetting out epoxy. I've used it many, many times without any problems, and have always had success with it. I’ve used it in the tug and barge market inside of voids and ballast tanks that were heavily corroded and have never seen a failure with it. After you have apply your zinc, come back and stripe coat the areas in question. Allow the 167 to dry for 12 to 24 hours, depending on the temperature. After the 167 has dried, start your next coat. I’ve use this product for over 20 years on 100s of vessels, and have seen the return of these vessel many times and have noticed no problems. This is an excellent product.
From
Stan Walker of Walker & Associates on
November 1, 2011:
The most successful method is to blast the total a ...read more
The most successful method is to blast the total area to be repainted as per the specification, usually a minimum of SSPC-SP 6. Prior to application of the zinc primer, apply a penetrating sealer (epoxy-based) into the joint and all areas of open back-to-back steel surfaces. After cure, reblast the flat surface areas around the areas where the penetrating sealer was applied to the original specification, then proceed with the zinc-epoxy-urethane system as specified. This method eliminates the failing of caulking systems and provides penetration of the joint areas not achieved with stripe coating suggestions. Stan Walker, Walker & Associates, Barrie, Ontario, Canada
From
Tim Lederer of The Sherwin-Williams Company on
October 25, 2011:
The crevices must be stripe-coated with the primer ...read more
The crevices must be stripe-coated with the primer by using a brush to work the coating into all voids.