Galvanized versus Painted Steel tanks

[Rick Murchison]

Arn't the painted tanks cold-galvinized and then painted? So would the question be is hot dipped galvinized better then cold-galvinized?

I don't think so. I believe they are acid washed, primed with an epoxy primer and painted with some really good stuff. The primer and paint are tough and a major pain to strip - but if rust gets started under there it'll win unless you catch it.
Rick

 

[Packhorse]

Are any fabers galvinised? Are galvinized tanks galvinized on the inside or just the outside? any reason why you cant hot dip galvinize a faber?
I just repainted a 3L Faber and it looked like it was galvinized but i was not sure. Anyway I used some cold galvinizing paint and then a few top coats of yellow.

 

[Rick Murchison]

Are galvinized tanks galvinized on the inside or just the outside? any reason why you cant hot dip galvinize a faber?

Just the outside.
I reckon you could strip and hot dip a Faber... all you need is the tank full of molten zinc big enough to dip it in
Rick

 

[MoonWrasse]

Are any fabers galvinised? Are galvinized tanks galvinized on the inside or just the outside? any reason why you cant hot dip galvinize a faber?
I just repainted a 3L Faber and it looked like it was galvinized but i was not sure. Anyway I used some cold galvinizing paint and then a few top coats of yellow.

I'm not so sure it's a good idea to galvinize the inside of a tank. Zinc is a heavy metal, and you can get poisoned from it. Welders know this.

 

[Hoosier]

Is the hot dipped galvinze process on Worthington HP tank recently upgraded to give more shiny looking?

 

[KidK9]

Very good thread...very informative.

 

[jonnythan]

Everything I know about galvanizing I learned from FredT. I think I have this all right, but please correct me if I'm wrong... and I haven't had my morning Dew yet, so it probably won't be overly coherent.

Galvanizing works because the zinc layer on the outside is a sacrificial anode. It also works because of electrical potential. When there's a scratch in the surface of the protective zinc coating, the zinc is absorbed into the surrounding water and then deposited on the surface of the scratch, recreating the protective coating over these scratches. I think it has something to do with being suberged in a conductive liquid, and the difference in potential induces a current, and the current causes the zinc to be plated to the exposed steel. Or something. But anyway.

This is all well and good for all tanks, until you realize that painting a tank ruins the galvanic action. The "protection" as it were depends on the large surface area of exposed zinc compared to the small surface area of exposed steel. Thus, scratches on tanks that have been galvanized and then painted rust whereas scratches on tanks that are only galvanized do not.

As for hot vs cold, hot-dipping is literally dipping the steel into a vat of molten zinc, as Rick mentioned. This yields a thicker, more durable, and more consistent coverage than does cold spray or painting or whatever it is that they do.

 

[jonnythan]

Oh yeah, and galvanizing the inside of a tank would be über-bad.

 

[captain]

Very interesting topic.

Arn't the painted tanks cold-galvinized and then painted? So would the question be is hot dipped galvinized better then cold-galvinized?

Cold galvanizing is basicly a paint coating with a lot of metalic zink in it. The zinc in it does provide some anodic protection but like any paint it can be scraped off. Hot dip galvanizing is a molecular bond of zink to the base metal (the tank) where the zinc moleules fuse with the steel molecules using heat similar to to the way heat is used to solder wires together. A much more durable and protective coating.

 

[Loneranger]

I have a set of steel Heisers that need to be stripped and painted after 3 years ( 180 dives). I got them at a steal of a price and they were kind of an experiment, but I would recommend painted steel for fresh water use only.