April 8, 2009

Sweating The Details

by Kevin Morris

Webster’s defines a specification as, “A particular and detailed description of a thing: specifically a statement of particulars describing the dimensions, details, or peculiarities of any work about to be undertaken as in architecture, building, engineering, etc.”

Today’s high performance coatings are more sophisticated than ever and require unique application techniques or equipment.  Labor rates are on the rise for the application of these types of coatings and lining systems and the products are designed to provide longer life cycles for the assets that they are protecting.

Yet, a large portion of premature coatings failures can be attributed precisely to the lack of details in specifications and most are easily noticeable with very little investigation. These details can be lumped into 2 categories: Visual and Non-Visual.

Visual details include terminations, penetrations, transitions, stripe coats, and inaccessible areas.

  • Terminations offer anchor points that prevent lifting or gouging of the coating/lining system or resistance to failure due thermal shock issues.
  • The sheer number of penetrations requires numerous methods of transitioning or terminating and should be evaluated based on each project.
  • Transition details can eliminate undue stress on a coating or lining system at the floor/wall transition or eliminate possible trip hazards on floor coatings.
  • Stripe coats offer necessary protection of sharp edges or angles where coatings have a natural tendency to shrink away.
  • Inaccessible areas like back-to-back angles or skip welds create voids that are impossible to properly prepare or coat.
Typical CAD Details

Typical CAD Details

Non-visual details are primarily related to surface contamination like chlorides or soluble salts.  In order to better understand the concerns with non-visual details you need to remember the four components of a corrosion cell: Anode, Cathode, Metallic Pathway, and an Electrolyte (commonly Water).

With all organic materials being permeable to a certain extent, the coatings act similar to a membrane and filter out the chlorides, making the electrolyte (water) pure and non- corrosive if it comes into contact with the substrate. Pure H2O contains no chlorides and will not conduct electricity between the anode and cathode. If chlorides remain on the surface or redeposit on the surface after surface prep and prior to coating application, the water that passed through the coating will come into contact with the chlorides and the corrosion cell can begin behind the coating/lining or create blisters. This process can take place on concrete as well, but is slightly different in the mechanics of the principle.

As you can see, small things that would add pennies on the dollar to a project’s total cost will contribute significantly to the life cycle of any applied high performance coating/lining system. Next time your ROI can be greatly increased if you “sweat the details”.

Other useful references are at:

McGraw Hill Construction Sweets Network for additional CAD details

PaintSquare’s Soluble Salt Technology Center

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