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

 

Download our free ebook on Ultra-High-Pressure Waterjetting

The case of…bubbles, and pinholes, and blisters, oh my!

From JPCL, September 2013

More items for Quality Control

by James D. Machen, PCS, KTA-Tator, Inc.
Richard Burgess, KTA-Tator, Inc., Series Editor

...
(Login to read the full article)

   

Tagged categories: Coating failure; Failure analysis; Moisture-cured polyurethane; Polyurethane; Power Plants

Comment from Harry Peters, (11/8/2013, 11:24 AM)

Emissions from coal-fired power generation plants are prevalently sulfur oxides which convert to sulfates when in contact with atmospheric moisture and not sulfides, since the sulfur containing coal is being burned (oxidized) to generate the power. Mild sulfuric acid "acid rain" deposits on steel, inducing the potential sulfate induced corrosion. The MCU Zn primer did exactly what it was supposed to as a sacrificial coating to protect the steel. It appears there was too much sulfate laden on the steel as the Zn reacted with the sulfate and subsequently reacted with atmospheric oxygen to form the white ZnO powder indicated, leaving the sulfate still present to corrode the steel. Given the environment, testing for nonvisible sulfates and removal during surface preparation would have prevented the coating failure.


Comment from William Feliciano, (11/8/2013, 3:18 PM)

I’m not certain that the sulfates are the only problem here. The MCU’s are notorious for outgassing, pinholing and bubbling, and i’ve seen many an MCU film wind up looking like swiss cheese once cured. Porosity of a topcoat in this situation can allow water and oxygen access to the primer, which can cause the Zn to "kick over" into ZnO powder. Though the Zn may be sacrificing itself as expected, it is doing it too soon and too quickly. This results in premature aging and/or failure of the system. Though MCU's are a good tool in the toolbox, they must be applied by competent contractors familiar with the technology. Specification, ambient conditions and recoat times must be respected just like with any other coating.


Comment from Car F., (11/25/2013, 12:36 PM)

Fascinating analysis and diagnosis,...thank you!!, I've learnt a lot this morning.


Comment Join the Conversation:

Sign in to our community to add your comments.

Fischer Technology Inc.
MP0R with rotating display screen

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


KTA-Tator, Inc. - Corporate Office
KTA-Tator EH&S Services

• Ambient & Worker Exposure Air Monitoring
• Safety & Health Program Development
• Lead Paint Assessments
& Specifications
• Health Hazard & Jobsite Safety Assessments
Call 1-800-245-6379


Elcometer, Inc.
New Elcometer 456 Coating Thickness Gauge

Best In Class Just Got Better. Technologically Intelligent And Robust. Marvelous Design And Durability. An Earth-Shattering Revolution In Coating Inspection.


Armorthane
Corrosion Coatings for Protection and Repair

Buy POLYURETHANE or POLYUREA coatings and spray surfaces for years of proven chemical resistance, water- and weather-proofing, and structural improvements.


Corrosion Probe, Inc.
From Detection to Correction

Corrosion Probe, Inc. has the Most Concrete Coatings Experience and Expertise. Contact us today at
860-767-4402, www.cpiengineering.com


Commercial Sandblasting & Painting Ltd.
Reliable Service & Superior Workmanship

We’re ready to meet any of your protective coating and lining needs. We can work on your site or in our facilities, with large shops (60,000 sq ft), 40 acres of yard space, and cranes and forklifts on site.


HoldTight Solutions Inc.
NO FLASH RUST -
NO CONTAMINANTS

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


Atlas Material Testing Technology

Helping You Put Your Products To The Test

• Outdoor Accelerated
Weathering
• Laboratory Testing
Services
• Accelerated Weathering
Instruments

www.atlas-mts.com atlas.info@ametek.com


Armakleen Company, The
ARMEX when nondestructive cleaning is critical

The gentle physical propriety of baking soda but yet aggressive cleaning ability is what makes ARMEX the only choice for nondestructive abrasive blasting.

 
 
 
 
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