Re: Dunois coating and organic sealant


Posted by Gordon England on August 05, 2003 at 12:25:10:

In Reply to: Dunois coating and organic sealant posted by jean claude Morizot on July 28, 2003 at 17:23:52:

: Hello,

: I use thermal sprayed 85/15 ZnAl alloy commercialy known as Dunois to protect stell toggles used in underground structure contruction when agressive soil conditions (high suphate and chloride content, sea water, 30 C temperature.....)are encoutered.

: Is it wise to add a sealant to Dunois coating ?
: Shall we actually observe a better durability of the anodic protection ?
: What type of sealant is recommended ?
: Is there any drawback ? what is happening when the scrificial anode coating is locally consumed ? Risk of local fast corrosion ?

: Thank you for your help

: JCM

This is a debatable issue. Sealing or applying organic paint systems on sacrificial coatings should increase the life of the coating, but may reduce the cathodic protection to areas where the substrate is exposed. Sealer/paint systems usually fail or become ineffective long before the zinc based coating gives up. So you could question the economics of applying a sealer/paint system compared to applying enough thickness of the zinc based coating to suit the time period of protection required.

Regards Gordon


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