Painting Galvanised steel. Yes or no ?

Poignard

Well-known member
Joined
23 Jul 2005
Messages
51,732
Location
London and Brittany
Visit site
The previous owner has removed blasted and galvanised the tabernacle. Is there any point in adding paint or is it better left bare. Any special primer/paint ( if 'yes' )
Thanks

About 13 years ago I had a new one made and galvanised. I painted it afterwards and it has lasted very well and it looks much better than bare galvanising.

I contacted International Paints Ltd and they gave me a schedule of what paints (theirs of course!) to use. I seem to remember it involved an etching primer followed by some 2-part paints. Cost a lot and I had to buy far more than I needed due to minimum pack sizes. Most of it is still in the garage waiting to explode. :eek:
 

prv

Well-known member
Joined
29 Nov 2009
Messages
37,363
Location
Southampton
Visit site
Mine's bare galvanised and seems to manage just fine with no treatment of any kind.

The inside got a dosing of sheep fat yesterday, but that was just to help the mast foot slide into place :D

Pete
 

Poignard

Well-known member
Joined
23 Jul 2005
Messages
51,732
Location
London and Brittany
Visit site
Just to be clear, I painted mine because I didn't like the look of the bare galvanising. I doubt the paint had much protective effect; it's just that ordinary paint doesn't adhere well to galvanised surfaces so a bit of special treatment is needed to make it last (which it certainly has done)

At least that's what the man who sold me the expensive paint told me :eek:
 

VicS

Well-known member
Joined
13 Jul 2002
Messages
48,318
Visit site
Provided the galvanizing is in good condition it is probably best left bare.

It can always be re-galvanized if necessary.

If painted then yes a suitable primer is necessary. Maybe, just maybe, Hammerite special metals primer.

Self etching primer was used for many years. No longer the preferred option for aluminium but may still be for galvanizing.

International have discontinued their self etch primer but still say to use one as a pre-primer under Interprotect ( 2 part epoxy primer) for galvanizing.

Paint is far more likely to be damaged than proper hot dip galvanizing.
 

Tranona

Well-known member
Joined
10 Nov 2007
Messages
41,211
Visit site
Painted mine and the mast band with Hammerite - special primer and normal silver top coat several years ago because it was looking a bit tatty after 40 years. Still looks OK. Would not bother if it is newly hot dipped - it will probably see you out (unless you are a youngster!)
 

MM5AHO

Well-known member
Joined
1 Oct 2007
Messages
2,517
Location
Central Scotland
Visit site
Painting galvanized steel has two effects. One is to prolong the corrosion resistance life of the coating system, and the other for aesthetics.
Galvanizing will last a long time, but that time is entirely dependent on the environment into which you put the steel.
Galvanizing protects by forming a skin of oxides and carbonates of zinc which in turn protect the zinc, which in turn electrolytically protects the steel. The oxide/carbonate layer re-forms if taken off by abrasion etc, but consumes some zinc in doing so.

To paint galvanized steel it is necessary (not optional) to etch the surface of the zinc first. There are several ways, but the simplest is to use a phosphoric acid brew often going by the name "T Wash". It's not strong acid, and contains some copper in order to turn the zinc black so that you know where you've treated and where you missed. After this dries, paint over the top with an alkyd, or epoxy paint. Disadvantage of epoxy is the lower UV resistance (breaks down in light).

"Hammerite" is not a type of paint, rather a brand. (in the same way that Dulux, Awlgrip etc are brands). Hammerite is owned by ICI, which in turn is owned by Akzo Nobel, the world's largest paint manufacturer.
Other Brands by Akzo include Awlgrip, Dulux, Glidden, Interlux, International Paints, Resicoat, Interpon, Chromadex, Sikkens, Trimetal and many others.
 

VicS

Well-known member
Joined
13 Jul 2002
Messages
48,318
Visit site
"Hammerite" is not a type of paint, rather a brand.

We know and both my post and Tranona's post referred specifically to Hammerite "Special Metals Primer". Which is a type of paint.
 

electrosys

New member
Joined
23 May 2009
Messages
2,414
Location
Boston - gateway to the North Sea (and bugger all
Visit site
Paint ? - yes - the function of the zinc coating is to protect the steel, if necessary by sacrificing itself in the process. So why not protect the zinc coating as well ?

I've painted my galvanised trailer with high-build zinc phosphate primer (although I'm sure any zinc-based primer would have done the same job), and expect it to easily out-live me ...
 

stewart9901

New member
Joined
8 Mar 2011
Messages
8
Visit site
I work on a boat that is 16yrs old, it has several galvanised parts on deck. these areas are still looking good even after the hard life they have had. as mentioned above, unless its the asthetics which are the problem itll be fine without paint.
 

DownWest

Well-known member
Joined
25 Dec 2007
Messages
13,164
Location
S.W. France
Visit site
One of the previous editors of PBO (G. Taylor? I lent the book and natch...) wrote a good tome on fitting out a bare hull. Good basic info on GRP work and other stuff, inc. galvanizing. He said that the sum of the protective effects of painting and galvanizing were more than their separate ones. So worth it. IIRR, there was no technical explanation of the effect.
But a galv. tabanacle looks OK on the right boat. I did see one that had wood laminated on....a real wood one would have been too clunky if strong enough.
 
Top