DNV-RP-B401, XYLAN coating breakdown factor
DNV-RP-B401, XYLAN coating breakdown factor
(OP)
Hi
I'm working on the design of a subsea product which is protected from corrosion by Cathodic Protection and paint/coatings.
I'm currently working through the DNV-RP-B401 calculation. Some of the component is coated with Xylan 1070, 20-50 microns thick. Am I right in thinking that the mean coating breakdown factor for this coating would be 1 i.e. equivalent to bare metal?
Regards
KMS
I'm working on the design of a subsea product which is protected from corrosion by Cathodic Protection and paint/coatings.
I'm currently working through the DNV-RP-B401 calculation. Some of the component is coated with Xylan 1070, 20-50 microns thick. Am I right in thinking that the mean coating breakdown factor for this coating would be 1 i.e. equivalent to bare metal?
Regards
KMS





RE: DNV-RP-B401, XYLAN coating breakdown factor
Steve Jones
Corrosion Management Consultant
http://www.linkedin.com/pub/8/83b/b04
All answers are personal opinions only and are in no way connected with any employer.
RE: DNV-RP-B401, XYLAN coating breakdown factor
Sorry-I missed out all the assumptions...
Design life=30 years
Depth=less than 30m
Assume that Xylan is a category 1 coating,so a and b=0.1
Mean coating breakdown factor=a+b*design life/2, which equals 1.6 but max is 1.
I think this means that the Xylan is not really considered to help as far as the calculation is concerned.
Is there any data out there for Xylan that shows that is better than a category 1 coating?
KMS
RE: DNV-RP-B401, XYLAN coating breakdown factor
Steve Jones
Corrosion Management Consultant
http://www.linkedin.com/pub/8/83b/b04
All answers are personal opinions only and are in no way connected with any employer.
RE: DNV-RP-B401, XYLAN coating breakdown factor
The Xylan coatings applied to fasteners are in the range of 20 to 50 micrometers, even for the thicker spray applied versions used in offshore environments. Long-term corrosion resistance of iron/steel components usually requires a sacrificial layer (e.g. zinc rich) plus an organic topcoat like Xylan. For subsea and cathodic protection, that changes things a bit. NORSOK M-001 says:
RE: DNV-RP-B401, XYLAN coating breakdown factor