| Connect Follow us on Twitter Like us on Facebook
About | Subscribe | Advertise


Download the latest free Blasting Resource Guide eResource Book

F-Files: Mechanisms of Failure
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.

DeFelsko Corporation
PosiTector Surface Profile

Two solutions for measuring peak-to-valley surface profile height with or without replica tape.

HoldTight Solutions Inc.

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

Novetas Solutions
Number 1 Crushed Glass Abrasive in America!

Manufactured from 100% Recycled Glass.
NO Crystalline Silica,
Beryllium & Arsenic
Great White Metal Finish!
4 plants on Navy QPL
Call us at 866-775-6226

The latest in Protective Coatings Technology

Examines every generic
type of protective coating
in detail, along with advantages and disadvantages of each. Add it to your library in print or ebook!

SEMicro Division, M.E. Taylor Engineering, Inc.
Coatings Adhesion Testers

The PATTI® accurately measures the bond strength between coating & substrate. Outfitted properly, the surface can be rough, porous, or curved & >10K psi strong!

Corrosion Probe, Inc.
From Detection to Correction

Corrosion Probe, Inc. has the Most Concrete Coatings Experience and Expertise. Contact us today at

KTA-Tator, Inc. - Corporate Office
KTA Analyzes
Coating Failures

• Field Diagnosis
• Lab Diagnosis
• Determination of Cause
• Recommendations
Call 1-800-245-6379

Fischer Technology Inc.

Paired with the PHASCOPE PMP10, Fischer’s new probe is quick and accurate for measuring thermally sprayed aluminum on stainless steel. Click to learn more.

Novatek Corporation
Novatek Corporation, Dustless Coatings Removal

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

SABRE Autonomous Solutions
Safety, Productivity, Quality. Robotic Blasting

Learn how this simple to use, field deployed, automatic robot is eliminating hazards in major confined, cluttered and complex surface preparation projects.

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   |   Privacy policy   |   Terms & conditions   |   Site Map   |   Search   |   Contact Us

© Copyright 2000-2016, 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