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
 
Clemco Industries Corp.
 
Maximum Dust Suppression Systems Start at $14,950
 
The system comprises proven technology and equipment with user-friendly flexibility in mind. See it in action.
 

 
Harsco
 
Find BLACK BEAUTY® Abrasives
 
Use our online tool to search by address, city or zip code to find where you can buy BLACK BEAUTY® abrasives. Or call us toll free: 1-888-733-3646
 

 
Vector Technologies Ltd.
 
The Original Performance Proven Vacuum Solutions
 
VecLoader® 616 Double Dump, Continuous Vacuum, 170 HP w/ 2,400 CFM & 28” Hg. 33% More Efficient than traditional vacuum systems! Choose Vector for the most powerful and the most reliable trailer mounted vacuums in the industry! Email us at: inquiry@vector-vacuums.com or call us at: 800-832-4010
 

 
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.
 

 
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
 

 
SABRE Autonomous Solutions
 
Repeatability
 
The ALPHA1 provides reliable results consistently allowing you to cost your next job with confidence.
 

 
Montipower, Inc.
 
The MBX Bristle Blaster
 
Get a 2.7 to 3.3 mil profile and a Near White Metal Clean. For info visit www.mbxit.com or call 877 629-8777
 

 
Novatek Corporation
 
Novatek Corporation, Dustless Coatings Removal
 
Strip, clean and profile all dust free! Comply with new lead standards. Contact today: (866) 563-7800
 

 
Bullard
 
Upgrade with the Bullard GenVX
 
Click here to learn how you can get a GenVX Helmet and Win.
 

 
DeFelsko Corporation
 
PosiTector SHD Shore Hardness Durometer
 
PosiTector SHD measures the hardness of non-metallic materials. Features a measurement timer, auto ignore mode and internal memory. Shore A or D available.
 

 
 
 

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