Contact US

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Floating roof tank coating to internal shell

Floating roof tank coating to internal shell

Floating roof tank coating to internal shell

In a floating roof tank we are using phenolic epoxy in first and top shell course and between them we are applying only zinc rich primer. Why is it ?
I am not aware about cargo to be stored for above tank as it is a query of friend of mine who dosen't know about cargo either.

RE: Floating roof tank coating to internal shell

My understanding is that zinc rich primer should only ever be the first coat as that is the only place it is advantageous and that's only on SSPC-6 or 10 metal. You don't get the galvanic benefits without a tight contact and the zinc primers don't have as good of adhesion in subsequent coats.

RE: Floating roof tank coating to internal shell

Dear Tugboat,

Here Question is not about overcoating phenolic epoxy with zinc.
Between first and top shells of floating roof tank, why zinc rich primer is applied on blast cleaned shell substrate.

I hope misinformation corrected.

RE: Floating roof tank coating to internal shell

Zinc rich primers provide a slight galvanic protection to the substrate. This requires a tight electrical connection which requires a blasted or acid etched surface. Other coatings and oxides prevent the galvanic connection. On our marine applications, we may specify two coats of International 300V (not zinc rich) as anti-corrosion coatings below the waterline as sacrificial anodes provide the galvanic corrosion protection. Above the waterline we use one coat of Interzinc 75V (zinc rich) topped with at least one coat of 300V. None of these are final coats.

Epoxy paints are highly sensitive to a few conditions including oil contamination and extended recoat intervals so of flaking is your issue I would start there.

RE: Floating roof tank coating to internal shell

Who knows the vagaries of the specifier? It would seem that more aggressive corrosion is expected at the first and top courses, whereas, in the intermediate courses, someone might have had the idea of simply stopping any light corrosion contaminating the product. Sometimes, end users are helpful in that they go some way to explaining why they specify what they do in the specification itself.

Steve Jones
Corrosion Management Consultant


All answers are personal opinions only and are in no way connected with any employer.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close