PaintSquare.com


The First Word in Protective & Marine Coatings

A Product of Technology Publishing / PaintSquare
JPCL | PaintSquare News | Durability + Design | Paint BidTracker


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)

 
   

Harsco
BLACK BEAUTY® App

Download the free app for BLACK BEAUTY® Abrasives. Explore all the features from the palm of your hand.
Toll Free: 1-888-733-3646


Polyval Coatings
Polyflex® Polyurea Linings

exhibit outstanding versatility in use; providing abrasion resistance, superior seamless waterproofing and high-chem corrosion protection. www.polyflexlinings.com


US Minerals
US Minerals -
Black Magnum

With nationwide production and distribution capabilities, U.S. Minerals supplies a complete range of coal slag and other abrasives to meet all of your blasting needs.


SAFE Systems, Inc.
Portable Blast &
Recovery Equipment

Trailer or skid mounted blast and recovery equipment. Systems designed for maximum versatility, environmental compliance
and overall cost savings.
Call 1-800-634-7278


GMA Garnet USA
GMA Garnet™
Natural Abrasives

- Superior cleaning
  performance
- Even Profile
- Low Dust
- Cost-Effective
- Environmentally friendly
- Recyclable up to 5 times
Tel : +1 832 243 9300


CESCO
PRESSURE PRO PRESSURE WASHERS

All types – All sizes to meet your every need.
Available to buy or rent. Shown-Model B5550HGEA511
• Cold Water • Pro Max
• Poly Belt • Gas
24 HP Honda Generator
CESCO Best Value $4065.00 Contact us: 888-772-3726 BlastandPaint.com


Fischer Technology Inc.
MP0R with rotating display screen

View your coating thickness readings from any angle with rotating display screen. New graphic display with easy menu navigation. Click for Video
Call 800-243-8417

 
 
 
Technology Publishing

The Technology Publishing Network

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

 
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 2000-2014, 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