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

 

Download our FREE eBook on New Technology Coatings for Corrosion Control

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.

KTA-Tator, Inc. - Corporate Office
KTA-Tator
Coatings Inspection

Any structure, any height, any place - A qualified coatings inspector is always available. Call 800-245-6379.


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


Elcometer, Inc.
Durability & Design meet
Performance & Reliability

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


U.S. Zinc
Historic Reliability. Innovative Performance.

As an industry leader with an established global footprint, we provide the products that prolong the life your paints and coatings. U.S. Zinc – Helping the world work™


Dampney Co., Inc.
Rubber In a can!

Rubberized Spray in a
Handy Aerosol Can

• Stays flexible
• Seals off moisture penetration
• Non sagging formulation
• Will not crack, chip or peel
• Apply to wet and dry surfaces
• Paintable


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


NLB Corporation
MiniARM automates surface prep

NLB’s Mini ARM lets an operator control high-pressure water jets remotely, with fast tool changes for different jobs. It maximizes protection and productivity.

 
 
 
 
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