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

 

Download our free e-book! Overcoating bridges and other structures.

Problem Solving Forum

| More

March 7 - March 13, 2011

When implementing an in-plant, exterior exposure, or accelerated testing program for coatings, should the test panels be scribed? Why?

More items for Program/Project Management


Selected Answers

From Joseph Schinner of Akzo Nobel Coatings Inc. on March 8, 2011:

     The real answer is the ubiquitous, "it depends." A more useable answer doesn't fit in a single sentence, so I will summarize the best I can. This response applies to coatings over metal, especially ferrous ("galvanized" or not) and aluminum. A scribe, whether vertical or an X-hatch, is a multi-tasker but has the common foundation of being a standardized form of scratch damage through a coating to the substrate. Sometimes a coating is only as good as it handles damaged areas, especially if damage is expected or unavoidable.

     Yes, there are coating/substrate situations where the coating looks great until a damage point is introduced, and the undercutting becomes so severe that the coating comes off in flakes or sheets. In a nutshell, the scribe provides a atarting point for undercutting of the film. This provides information on film adhesion under test conditions (especially wet film adhesion in humidity conditions).

     The old-fashioned knife point dig at the middle of the X-hatch is still used to show inherent adhesion. It also is a negative control area to show the conditon is sufficient to cause corrosion (in the scribe)and coating protection is needed. The corollary is that it shows the effectiveness of the passivation or sacrificial effects of a corrosion inhibitor to prevent undercutting. Without using some sort of damage areas when doing accelerated testing, the test itself could be grossly misleading to the positive side. Some testers use direct or reverse impact, with or without cross-hatch scribing instead. Some use impact AND scribe- it all depends on damage expected and tested for. A scribe can be used for most accelerated testing, but practicality dictates where it is more beneficial: salt fog, cyclic corrosion testing, real time Emmaqua®, Florida, etc. It sometimes is used with water fog and Cleveland condensing humidity, but these tests are specifically for blister resistance where a scribe is not necessary if the other environments are used. Sometimes, even the QUV, Weather-Ometer® panels are scribed, but common sense here dictates caution because these are primarily gloss/color drift tests that a scribe interferes with on small panels. Bottom line: it is usually best to incorporate a scribe in test procedure somewhere. 

From Lee Edelman of Independant on March 8, 2011:
     Yes, scribes shouold be used to test for rust creepage.  
The test panel needs to be scribed, and the surface needs to be exposed to the corrosive elements. Undercutting  and adhesion need to be checked.

Please sign in to submit your answer this question    

Tagged categories: Maintenance programs


Current PSF Question | Submit a PSF Question | Full PSF Archive

Industrial Vacuum Equipment Corp.
Hurricane Vacuums
& Dust Collectors

Vacuum and dust collector hose, filters and related accessories.
IndustrialVacuum.com


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


Atlantic Design, Inc.
CLICK HERE

to see what we did to this dust collector! ADI can increase the efficiency and life of your equipment! Any brand, for less than new! 866.Call.ADI


HoldTight Solutions Inc.
NO FLASH RUST - NO CONTAMINANTS

Our HoldTight®102 salt remover & flash rust
preventer prevents flash
rust by removing surface contaminants. Contact us
for your nearest distributor.
(800) 319.8802 sales@holdtight.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.


Polygon
POLYGON - Temporary Humidity Control

We specialize in innovative climate control solutions for industrial painting, utilizing alternative energy sources and combining desiccants with heating or cooling.


Fischer Technology Inc.
MP0R with rotating display screen

Automatic rotating display screen just like your smart phone. Click for Video
Call 800-243-8417


Safway Services
Your Access Advantage. QUIKDECK®

Provides safe, factory-floor-like working conditions. Can be engineered to fit almost any shape, structure or size. Modular platform easily assembled from just a few basic components. Excellent containment. Applications include vessels, offshore rigs and bridges.


Sherwin-Williams
Sherwin-Williams General Polymers Resinous Flooring App

Our coatings and linings expertise available 24/7, allowing you to explore the Sherwin-Williams systems best suited for your flooring needs. Android Users Click here to Download the app today!


DRYCO
Humidity & Temperature Control Equipment

Rental Desiccant Dehumidifiers, ArcticDRY Units, Air Conditioners, Heaters and Generators to help control the climate on your next industrial painting project. Nationwide locations, 24/7 service: (866) 379-2600 www.drycogroup.com”

 
 
 

Technology Publishing Co., 2100 Wharton Street, Suite 310, Pittsburgh PA 15203-1951

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