PaintSquare.com
Follow us on Twitter Follow us on LinkedIn Like us on Facebook Follow us on Instagram Visit the TPC Store
Search the site

 


G84 Standard Practice for Measurement of Time-of-Wetness on Surfaces Exposed to Wetting Conditions as in Atmospheric Corrosion Testing

All Standards | ASTM Standards
Search Standards


Click to Purchase and Download this Standard or Test Method

Revision Date: April 03, 2012
Updated On: April 04, 2012
Editorial Change:
 
This practice provides a methodology for measuring the duration of wetness on a sensing element mounted on a surface in a location of interest. Experience has shown that the sensing element reacts to factors that cause wetness in the same manner as the surface on which it is mounted.

Surface moisture plays a critical role in the corrosion of metals and the deterioration of nonmetallics. The deposition of moisture on a surface can be caused by atmospheric or climatic phenomena such as direct precipitation of rain or snow, condensation, the deliquescence (or at least the hygroscopic nature) of corrosion products or salt deposits on the surface, and others. A measure of atmospheric or climatic factors responsible for moisture deposition does not necessarily give an accurate indication of the TOW. For example, the surface temperature of an object may be above or below both the ambient and the dew point temperatures. As a result condensation will occur without an ambient meteorological indication that a surface has been subjected to a condensation cycle.

Structural design factors and orientation can be responsible for temperature differences and the consequent effect on TOW as discussed in 4.2. As a result, some surfaces may be shielded from rain or snow fall; drainage may be facilitated or prevented from given areas, and so forth. Therefore various components of a structure can be expected to perform differently depending on mass, orientation, air flow patterns, and so forth. A knowledge of TOW at different points on large structures can be useful in the interpretation of corrosion or other testing results.

In order to improve comparison of data obtained from test locations separated on a macrogeographical basis, a uniform orientation of sensor elements boldly exposed in the direction of the prevailing wind, at an angle of 30° above the horizontal is recommended. Elevation of the sensor above ground level should be recorded.

Although this method does not develop relationships between TOW and levels of ambient relative humidity (RH), long term studies have been carried out to show that the TOW experienced annually by panels exposed under standard conditions is equivalent to the cumulative time the RH is above a given threshold value. This time value varies with location and with other factors. Probability curves have been developed for top and bottom surfaces of a standard panel at one location which show the probable times that a surface will be wet as a percentage of the cumulative time the relative humidity is at specific levels. If needed, it should be possible to develop similar relationships to deal with other exposure conditions.

(Back to all Standards)

 
   
Advertisements
 
SEMicro Division, M.E. Taylor Engineering, Inc.
 
Coatings Adhesion Testers
 
The PATTI® accurately measures the bond strength between coating & substrate. Outfitted properly, the surface can be rough, porous, or curved & >10K psi strong!
 

 
Monti Tools, Inc.
 
BRISTLE BLASTER® – THE ORIGINAL ONE
 
  • Abrasive blast with a power tool
  • Remove corrosion, mill scale and coatings
  • Cleans & roughens
  • Meets SSPC-SP 10 / NACE No. 2
  • Profile up to 4.7 mils
  • ATEX Zone 1
  •  

     
    Fischer Technology Inc.
     
    NEW Protective Coating Inspection Website
     
    Click Here!
     

     
    BASF
     
    New resins from BASF will have metals loving water!
     
    Excellent corrosion resistance, low VOC, high gloss, thin films www.basf.us/industrialcoatings dpsolutions@basf.com 800-231-7868
     

     
    Tnemec Company, Inc.
     
    Online Coating Courses from Tnemec
     
    For decades, Tnemec has offered its expertise to clients presenting face-to-face coatings courses. Now, these presentations are available to anyone for CEUs at Tnemec University.
     

     
    Advanced Recycling Systems
     
    ARS Blast Vacuum Recycling System
     
    • Closed loop vacuuming eliminates multi-handling of blasting media and wastes.
    • Abrasive waste reduced by 98%
    • Process between one and fifteen tons of media per hour.
     

     
    CHLOR*RID International Inc.
     
    SOLUTIONS THAT WORK
     
    Companies that invest in corrosion control use CHLOR RID products
    • Soluble salt removal liquid
    • Test kits to verify contamination levels
    • Surface passivation to hold the blast
    INFO@CHLOR-RID.COM 800.422.3217
     

     
    Absolute Equipment/Grand Rental Station
     
    TIER 4 EQUIPMENT
     
    We have Tier 4 Equipment including Air Compressors & Generators for Sale & Rent! Your job may now require Tier-4. www.absoluteequip.com or Call 412-931-6655.
     

     
    PPG Protective and Marine Coatings Group
     
    We Protect and Beautify the World
     
    PPG is widely recognized as a world leader in protective and marine coatings, developing innovative, cutting-edge products and services.
     

     
    Detail Masters
     
    Overspray Removal
     
    We offer professional, turnkey service and unparalleled quality!
    Our process can save hundreds— even thousands of dollars. It's fast, environmentally safe and 100% guaranteed.
     

     
     
     

    Technology Publishing Co., 1501 Reedsdale Street, Suite 2008, Pittsburgh, PA 15233

    TEL 1-412-431-8300  • FAX  1-412-431-5428  •  EMAIL webmaster@paintsquare.com


    The Technology Publishing Network

    Durability + Design PaintSquare the Journal of Protective Coatings & Linings Paint BidTracker

     
    EXPLORE:      JPCL   |   PaintSquare News   |   Interact   |   Buying Guides   |   Webinars   |   Resources   |   Classifieds
    REGISTER AND SUBSCRIBE:      Free PaintSquare Registration   |   Subscribe to JPCL   |   Subscribe to PaintSquare News
    MORE:      About PaintSquare.com   |   Privacy policy   |   Terms & conditions   |   Site Map   |   Search   |   Contact Us