Steel protectiom in the marine environment.

Scotty_Tradewind

Scotty_Tradewind

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Me: South Oxfordshire. Boat, Galicia NW Spain
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I've just used some of Halfords rust remover (contains Hydrochloric and phosphoric acids)on the base of my king post after chipping and hammering off the excess rust after 30+ yrs.
After a couple of trys it came up as clean as new steel.
I washed off and dried, then applied some Zinga zinc paint which I'm advised should be good to prevent more rusting, which can then be painted over the top. see.........
http://www.zinga-uk.com/?gclid=CKTqt96CzKgCFQEKfAodZn5Mrg

I'll report back at the end of the season to say if it's worked.
 
Could be timely; I was just derusting an anchor and considering if it was worth doing a really good job or just a descale and hamerite.
I suppose I could also have it blasted and galvanised but is it worth it?
What is the best treatment?
The technical write up on that Zinga sounds quite believable
 
Zinga is a good zinc rich paint. It has a high zinc content in the dry film.
But a disadvantage of any zinc rich paint is that the zinc particles are not in electrical contact with each other. This contact is required in order to give proper elctrolytic protection. Zinc rich paints have a binder, which is non-conducting, and so insulates the particles from each other and from the base metal.
Contrast that with galvanizing, which is pure (well nearly pure) zinc, metallurically alloyed to the steel, in full electrical contact with the metal and has itself full electrical conductivity, being a continuous layer of metal.
Both Zinga and galvanizing also give barrier protection for as long as the barrier is not perforated. Its far easier to perforate a painted coating than to perforate galvanizing.


But salt water corrosivity is very variable with several factors. One is location. For example in salt water in the Arabian sea, the corrosivity is far higher than in the north Atlantic.
And depth has quite an influence too. The splash zone is worst, thenthe deeper the item, the lower the corrosion.

edit:
see also the following: http://www.galvanizeit.org/images/u...h_Paint_vs._Hot-Dip_Galvanizing_(5-4-06)_.pdf
 
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pcatterall said:
Could be timely; I was just derusting an anchor and considering if it was worth doing a really good job or just a descale and hamerite.
I suppose I could also have it blasted and galvanised but is it worth it?
What is the best treatment?
The technical write up on that Zinga sounds quite believable
Click to expand...

My friend drilled a new hole through the shank of his galvanised anchor to take a pin to hold it on the roller.
He used Zinga on the freshly drilled hole and it has not rusted after one season.
The Zinga painted hole surface is very probably going to break down after some time especially with the movement of the anchor on the pin,, but even if he has to clean and paint that small area each season, it is well worth it he thinks rather than the cost of regalvanising.
 
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''But a disadvantage of any zinc rich paint is that the zinc particles are not in electrical contact with each other''.
Ahh ! the Zinga blurb suggests that there is electrical contact rather than just being a sacrificial coat and barrier. It claims that it will effectivly protect quite wide damaged areas. Perhaps this is all just sales talk?
 
I've tried just about every steel treatment going, on my mild steel lifting keel plate.

By far the best results have been with Dulux Metalshield.

It's one-part, but does require its' own primer; as I always say to people, don't laugh at the 'Dulux' bit, this stuff is the business !

Roughly £20 a tin for primer & paint each, available from good paint/DIY places like Brewers.

Sadly, I'm not on commission...
 
KellysEye said:
> Perhaps this is all just sales talk?

No it's true, always apply zinc rich primer to bare steel, it works.
Click to expand...

Yes that's understood; the zinc in that case acts in sacrificial manner but there is also a potential eloctrolytic aspect/benifit which is not active in a simple primmer/barrier application. Thats what is claimed in the technical blurb for this product.
 
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