PaintSquare.com
Follow us on Twitter Follow us on LinkedIn Like us on Facebook Follow us on Instagram Visit the TPC Store
Search the site

 

Advertisement

PaintSquare


Problem Solving Forum

| More

November 11 - November 15, 2013

I have galvanized steel in direct contact with powder-coated aluminum in an outdoor exposure. The galvanized steel is corroding. What is the best way to remedy the situation?

More items for Quality Control


Selected Answers

From Robert Cameron of Belzona Houston on November 22, 2013:
There are two-part epoxies available that are tolerant to surface contaminants. I would remove loose contaminants with hand tools and even refer to SSPC-SP 11, Power Tool Cleaning to Bare Metal, if possible on the galvanized section (no need to knock off the galvanized layer if it is tightly adhered). Then mask the powder-coated area, and apply two coats of this two-part, surface- tolerant epoxy.

From Karen Fischer of Amstar of Western New York, Inc. on November 19, 2013:
Though there isn't much information here as to what kind of structure this might be and how the two materials are connected (fixed or movable), my first inclination would be to isolate the two dissimilar metals with a neutral, non-reactive material of some kind to eliminate the direct contact between these two metals. Clearly, the galvanized metal is reacting with the powder-coated material. I don't know what kind of structure this is, but some type of rubber or plastic spacer may be enough to stop this reaction. Painting of the galvanized metal may not provide sufficient isolation, especially if the connection is movable. Repair and re-galvanizing the corroded area can then be accomplished.

From Carl Thompson of Hill Brothers on November 11, 2013:
I would tape the powder-coated aluminum where it meets the steel. Aluminum is amphoteric and can be attacked by either acid or alkali. Treat the galvanized steel with a 20% solution of phosphoric acid. Wait 15 minutes, then wipe the rust and corrosion away. If some corrosion remains, repeat the process. When cleaned, neutralize the galvanized steel with a very dilute solution of ammonia. You should see a white residue on the surface . This is an oxide of phosphoric and should help keep further corrosion away. Any holes developed from corrosion should be filled with a metallic, 2-part epoxy putty. If painting is desired, brush away any loose white powder with a stiff copper brush and proceed. To prevent any galvanic reaction between the aluminum and the stainless steel, painting the galvanized metal would be preferred.

Please sign in to submit your answer this question    

Tagged categories: Aluminum; Corrosion; Galvanized steel


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

Advertisements
 
DeFelsko Corporation
 
PosiTector SST Soluble Salt Tester
 
Measures the concentration of soluble salts on metal surfaces. Use with all Bresle patch types including the reusable, adhesive-free PosiPatch.
 

 
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
 

 
Detail Masters
 
Overspray Removal
 
We offer professional, turnkey service and unparalleled quality!
Our process can save hundreds— even thousands of dollars. It's fast, environmentally safe and 100% guaranteed.
 

 
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!
 

 
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 1-800-532-3633
 

 
Termarust Technologies
 
Termarust (HR CSA) Chemically Stops
Active Corrosion
 
Arch truss treated with Termarust's (HR CSA) in 2003. This steel arch bridge is rust free on all surfaces including the crevice corroded joints and connections.
 

 
Fischer Technology Inc.
 
NEW PROBE FOR MEASURING TSA THICKNESS
 
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.
 

 
Tnemec Company, Inc.
 
Online Coating Courses from Tnemec
 
For decades, Tnemec has offered its expertise to clients presenting face-to-face coatings courses. Now, these presentations are available to anyone for CEUs at Tnemec University.
 

 
Jotun Paints Inc.
 
Jotun Jotachar 1709
 
Mesh-free passive fire protection epoxy designed to protect against hydrocarbon pool fire scenarios for up to four hours as defined in the ANSI/UL1709 standard.
 

 
Absolute Equipment/Grand Rental Station
 
TIER 4 EQUIPMENT
 
We have Tier 4 Equipment including Air Compressors & Generators for Sale & Rent! Your job may now require Tier-4. www.absoluteequip.com or Call 412-931-6655.
 

 
 
 

Technology Publishing Co., 1501 Reedsdale Street, Suite 2008, Pittsburgh, PA 15233

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