Hot dip galvanizing vs Cold galvanizing spray

[Mountain132]

Has anyone used a zinc galvanizing spray or paint in the past 10+ years that can comment on the rusting of the steel? The article attached in the link annotates the differences fully noting that hot dipping is the preferred method.

http://www.galvanizeit.org/images/uploads/articles/FTL_08_2006.pdf

[KevinNY]

Good quality cold galvy zinc spray, like ArcAir brand at welding supply places, holds up very well. Obviously not as good as being dipped, but pretty darn good.

[yorker]

The zinc spray paint can work surprisingly well, I did a hitch in it 10-13 years ago and it is just now starting to rust through. I don't remember what brand I got- I picked up a case from an army surplus dealer.

[Mountain132]

The zinc spray paint can work surprisingly well, I did a hitch in it 10-13 years ago and it is just now starting to rust through. I don't remember what brand I got- I picked up a case from an army surplus dealer.

surface rust or rust totally through?

[leafsprung]

"cold galvanizing" is a different process. It does not bond to the base metal. Its just fancy paint.

[SafeAirOne]

"cold galvanizing" is a different process. It does not bond to the base metal. Its just fancy paint.

I was sitting back and watching this thread and thinking the same thing. After reading Yorker's post, I would love to hear more independent testimonials for the spray-on "galvanizing" stuff. 10-13 years is pretty decent, providing the item in question wasn't garaged every winter...

[Broadstone]

In my line of work we often must use the cold Galv. spray when welding galv material such as handrails, dunnage iron which supports airconditioning units, benches, canopies and lintels supporting brick. Truth is even when applied properly it is a noticable difference. (If you know what you are looking at) I agree that it could last quite a few years but will become visable with surface rust beginning to bleed through. If someone were to think they could cold galv a chassis the downfall would be the inside of it. Where any protective material cannot be properly applied you are wasting time doing anything. Just as waxoyl in my opinion is a waste of time and effort if applied only to the exterior of the chassis. In my opinion they each have their place. I cold galved all the tub trim 6 years ago then clearcoated and it looks as good as the day I applied it. I also however on my current project hot dipped everything I never want to repair for the next 75 years!!

[yorker]

I was sitting back and watching this thread and thinking the same thing. After reading Yorker's post, I would love to hear more independent testimonials for the spray-on "galvanizing" stuff. 10-13 years is pretty decent, providing the item in question wasn't garaged every winter...


It is never garaged and since it is a hitch it has been subject to salt spray etc. I have really been surprised how well it worked- I had only intended it to be a short term solution- but you know how that goes. Who knows maybe if I use Rustoleum it would have lasted just as well?:sly:

It exceeded my expectations by a large margin.

I don't think it is a substitute for real galvanizing- but it works better than you might think considering it is just fancy paint.

[Metallisation]

Just to throw another great option into the ring, there is a process called metal spraying (also known as thermal spraying or zinc spraying). This process uses equipment to melt zinc (or aluminium or many other materials) wire, atomise it and project it onto the item to be sprayed. The result is a pure metal coating which offers the same protection as hot dip galvanise (or sometimes better as you can put thicker metal sprayed coatings on - up to several mm if required but 150-250 microns is more normal). The main benefit is that it is a metallurgically cold process so you don't get heat distortion which can cause problems with hot dip galving chassis' for example.

You need to grit blast the surface clean before hand and it is line of sight so you will still need to waxoyl the internals of a chassis for example. However, as a process it's very well proven and has been used to protect anything from fences, playground equipment right up to offshore platforms and the recently opened Burj Khalif tower in Dubai.

It's not really a DIY process but there are plenty of companies dotted around the world doing it as an alternative to hot dip galv.

Sorry for the sales type pitch - not intended but I have built a 100" hybrid LR in the past and wished I'd known about this before having to straighten out my chassis after having it galved!

Happy Land-Rovering - wife and kids forced sale of mine but I still yearn to get back to it one day.

[Jim-ME]

Is there a company that does this in New England?
Jim

[leafsprung]

The result is a pure metal coating which offers the same protection as hot dip galvanise

There are some big drawbacks to metalized zinc spray. The hardness of the resulting coating and the bond strength of the coating to the steel are much less than with hot dip galvanizing. Hollow sections are not protected at all and it costs much more. It is far less effective.

[Metallisation]

In the interests of clarity, I'd like to respond as impartially as possible to the Leafsprung post.

Metallised zinc spray is not all things to all men and neither is hot dip galvanising. There are benefits of both. Some applications would favour metal spray, some favour hot dip and there is also a considerable cross-over in the middle.

Hardness of the coating is very dependent on the steel substrate when hot dip galvanising. If the steel has a low silicone content, then the interface layer between the steel and the galv will be hard but the zinc on top will be just pure zinc. If there is a lot of silicone in the steel, it will produce a very hard galv coating but this will also be brittle which is not good either. Metal spray is effectively a pure zinc coating and has the hardness of zinc.

Metal sprayed zinc bond strength is not as high as properly applied hot dip galv but it is around 5MPa (725psi) and I challenge anyone to select their largest landrover hammer and remove it - so not as well bonded but still bonded well enough (good enough for offshore oil platforms, security barriers, fishing boats etc.

I did mention that it's a line of sight process so it will not coat the internals.

As to cost, it can be cheaper, it can be more expensive - it is very much application dependent and what is important to you. Also depends on if you include the cost of correcting heat distortion in your calculation for example or grinding off spikes and runs, re-drilling / tapping holes etc.

I only mentioned it as a well accepted alternative to hot dip which is widely used in many industries.

Regarding a New England applicator, please contact our distributor in the USA via http://www.tmsmetalizing.com/ - I'm sure they'll be able to put you in touch with someone.

[leafsprung]

In the interests of clarity, I'd like to respond as impartially as possible

Probably going to be difficult to be impartial when you work in the industry, are actively advertising your process and have the user-name "metalisation":rolleyes: (its actually a "Z" in there.)



Hardness of the coating is very dependent on the steel substrate when hot dip galvanising. If the steel has a low silicone content . .

Silicone is for hollywood types trying to get ahead, silcon is a steel constituent. :rolleyes: There is not really any cold rolled, high silicon content steel in the items you would galvanize on a land rover, so you dont have issues here with hot dip.


Metal sprayed zinc bond strength is not as high as properly applied hot dip galv but it is around 5MPa (725psi) so not as well bonded but still bonded well enough (good enough for offshore oil platforms, security barriers, fishing boats etc.

The bond strength of hot dip is more than triple metalized zinc spray. The bond strength is largely mechanical for metalized zinc spray. The service life of hot dip galvanizing is longer in every environment. The only reason you see metalized zinc spray on large installations is because they are too big to fit in a tank to hot dip them.


I did mention that it's a line of sight process so it will not coat the internals.

Land rovers rust from the hollow spaces outwards, with no protection in the hollow spaces means metalized zinc spray is next to worthless. I would honestly rather have a painted frame than a metalized zinc sprayed frame. The same level of maintenance is required to keep it from rotting away.


As to cost, it can be cheaper, it can be more expensive. Also depends on if you include the cost of correcting heat distortion in your calculation for example or grinding off spikes and runs, re-drilling / tapping holes etc.

Every land rover chassis manufacturer including the factory have used galvanizing to protect their frames, if the risk of distortion and cost of cleanup were so high, do you think they would bother? Metalization is always FAR more expensive. Initially its more expensive to have it done because its more labor intensive and long term its more expensive when your chassis rusts away anyway because the important parts havent got any coating on them . . .

[yorker]

Probably going to be difficult to be impartial when you work in the industry, are actively advertising your process and have the user-name "metalisation":rolleyes: (its actually a "Z" in there.)

. . .


http://www.metallisation.com/

[leafsprung]

:D ..

[meatblanket]

Silicone is for hollywood types trying to get ahead.

:thumb-up: