Painting and anodes???
Painting and anodes???
(OP)
Hope you can offer some badly needed advice
During a discussion it was mentioned that you always paint the underside of anodes, the side adjacent to the stucture. Do you have any specifications, codes or litreture to prove why this is done, the advantages / disadvantages etc..
We are being asked why we paint the underside of anodes and I am having great difficulty in producing any justification as to why we do this.
It maybe coded somewhere or a general rule of thumb!
Do you then adjust the cathodic protection calc to remove the painted surface area?
Can you help with any information on this topic.
Best Regards
Greig
During a discussion it was mentioned that you always paint the underside of anodes, the side adjacent to the stucture. Do you have any specifications, codes or litreture to prove why this is done, the advantages / disadvantages etc..
We are being asked why we paint the underside of anodes and I am having great difficulty in producing any justification as to why we do this.
It maybe coded somewhere or a general rule of thumb!
Do you then adjust the cathodic protection calc to remove the painted surface area?
Can you help with any information on this topic.
Best Regards
Greig





RE: Painting and anodes???
Never specified; no rule-of-thumb. In fact, the primary guidance is one contained in both cathodic protection and painting references - DO NOT PAINT ANODES.
RE: Painting and anodes???
RE: Painting and anodes???
Steve Jones
Materials & Corrosion Engineer
http://www.pdo.co.om/pdo/
RE: Painting and anodes???
We are fabricating subsea structures which are painted with 350 to 450mic of epoxy highbuild and also have flush fitting and stand off type anodes.
We currently paint the steel underneath the anode and don't apply any coating at all to any of the stand off anodes, but coat the underside of the flush fits.
Do you guys think this is acceptable? Opinions please.
RE: Painting and anodes???
WHY is this a requirement?
I would imagine it's because coating damage is likely under the anode, and this damaged area will then contribute to the load on the anode, shortening the life of the anode.
However, I can't imagine this decrease being significant, especially if a good quality durable coating is used to protect the structure (A BIG assumption, I admit).
Bottom line(s):
(1) If coating the underside of flush-mounted anodes is the current standard practice, I wouldn't change.
(2) If current procedures do not coat the undersides, I wouldn't change.
(3) I doubt a cost-benefit analysis would support coating the undersides, but that's just an opinion off the top of my head.
RE: Painting and anodes???
RE: Painting and anodes???
RE: Painting and anodes???
It could be nothing to do with proximity (can't find any data) but this may explain (or rather NOT explain) why you do it.
Never Assume, you make an Ass out of U and Me
RE: Painting and anodes???
RE: Painting and anodes???
I have no knowlage of how the existing paint scheme was applied so the fault could lie there, it just seemed odd that the blistering was localised around the Anodes.
This is even more puzzling as the old Anodes were Zinc but the water was brackish so they would (and had) quickly become useless due to the surface becoming non conductive.
Never Assume, you make an Ass out of U and Me
RE: Painting and anodes???
RE: Painting and anodes???
Could it be that, you heard it as "the hull structure which would stay underneath of anode, has to be painted" ???
I assume it is so, and the reason is so simple, we paint the area which the anode will be fitted upon it, beacuse after welding the anode to the hull, then it will be impossible to apply the paint undertneath the anode.
Hope this is the answer you need.
GOKHAN
Naval Arc.& Marine Eng.
RE: Painting and anodes???
Two things I read in this that I need to dispute. Most anodes are manufactured with the bar running through it in such away that the corroding anode will not "fall off" until it is almost gone, probably 20% or less left of the anode.
Secondly, to say that you would do something to increase the life of the anode is not what you want to achieve. Increasing the life of the anode means that it isnt giving maximum protection to the structure it is supposed to be protecting.
If you want to get more info on this, I would get a hold of the guys at Wilson Walton. Google them and it will give you the website with contact info.