PaintSquare.com
      | Connect Follow us on Twitter Like us on Facebook
About | Subscribe | Advertise
  

 


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)

 
   

Abrasives Inc.
See the difference immediately Black Magic®

Quality blast abrasive goes farther. Use Black Magic® The Tough Stuff coal slag. Cleaner, consistent, less dust. Order yours today!
Abrasives Inc. 800-584-7524


LS Industries
LS Blasters: Optimum Steel Cleaning Efficiency

Simplify surface prep with the precise shot control of LS Blasters. Our blast technology delivers optimum coverage and finish. 800-533-8008


Armakleen Company, The
ARMEX when nondestructive cleaning is critical

When cleaning substrates that cannot be damaged the only blast abrasive to use is ARMEX. Other blast abrasives can remove surface materials damaging the substrate.


U.S. Zinc
Historic Reliability. Innovative Performance.

For 65 years, the success of U.S. Zinc has come from the quality of our people and our products. The protection properties of our zinc dust prolong the life of marine coatings, helping the world work™


SAFE Systems, Inc.
Custom blast rooms
by SAFE Systems

Don't waste time and money "making do" with a "standard" design. Let us work with you to design and build the
system that best fits
your requirements.
Call 1-800-634-7278


Termarust Technologies
Termarust (HR CSA) Chemically Stops
Active Corrosion

Truss bridge treated with Termarust's (HR CSA) in 1995. This highway & rail truss bridge is still stable and there still is no active corrosion.


Advanced Recycling Systems
ADVANCED RECYCLING SYSTEMS (ARS)

Recycling Machines, Dust Collectors, Rapid Deployment units are time-tested and approved for the rugged industrial environment. Contact ARS today!
(330)536-8210


Elcometer, Inc.
Durability & Design meet
Performance & Reliability

Elcometer 319 Dewpoint Meter
View the technical data on the Elcometer Dewpoint meter.


Axxiom Manufacturing
Revolutionary Units

By integrating Schmidt's Aftercoolers with our blast pots, these systems remove moisture from air and minimize equipment footprint on jobsite.
Call 1-800-231-2085

 
 
 
Technology Publishing

The Technology Publishing Network

The Journal of Protective Coatings & Linings (JPCL) PaintSquare
Durability + Design 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
 

© Copyright 2000-2015, Technology Publishing / PaintSquare, All rights reserved
2100 Wharton Street, Suite 310, Pittsburgh PA 15203-1951; Tel 1-412-431-8300; Fax 1-412-431-5428; E-mail webmaster@paintsquare.com