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  #1  
Old October 28th, 2009, 03:53 PM
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Galvanizing question

Has anyone out there tried just galvanizing a complete door (roll-up) vs. taking the door frame completly apart, having it treated then galvanized the frame and then reassemblying the whole thing.

Once galvanized, aside from the obvious surface prep for priming and painting, isnt this a more cost effective and potentially more effective rust prevention?

Thoughts? Experiences?
Mark
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  #2  
Old October 28th, 2009, 04:18 PM
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Up until recently, all of the LR doors had aluminum skins which would melt in the zinc bath.
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  #3  
Old October 28th, 2009, 04:21 PM
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Door Dip

Hi Paul, Thanks for the reply. Yes, should have mentioned, I'm thinking of getting hold of those new generation doors for a total Dip. What do you think?
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Old October 28th, 2009, 04:34 PM
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Perhaps someone else has a definite answer, but I thought that the new type doors (2006+) were already galvanized.
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  #5  
Old October 28th, 2009, 04:37 PM
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Well, I was wondering about that too. If the upper and lower sections are or if just the lower section is.

Anyone?
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  #6  
Old October 28th, 2009, 04:50 PM
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Speaking of Zinc...is it possible just to fasten zinc bars to the bare aluminum, say on the inside of a door. Much like they do for marine applications.

Would this slow done or even stop the process of rot on the door?

just a silly thought...
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  #7  
Old October 28th, 2009, 05:06 PM
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The flat parts would come out all wavy. JimC gave me a set of galvy door frames and I plan to reskin them in the future.
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Old October 28th, 2009, 06:16 PM
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For the record, the melting point of aluminum is over 1200 degrees, and the zinc bath is around 800, so while aluminum skins won't melt, they would be utterly destroyed.

And bathing the all-steel door would also be a bad idea. The skins would warp badly, and no amount of filler would flatten them out. Additionally, the zinc would probably leave unprotected pockets inside the doors. Unless all the air comes out perfectly, then the zinc can't get there. Lastly, there are adhesives and stuff used in the door that the galvanizer would probably not like to put in his tanks.
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  #9  
Old October 28th, 2009, 07:54 PM
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Bad idea

Back to the drawing board
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  #10  
Old October 28th, 2009, 09:33 PM
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how about using epoxy?
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  #11  
Old October 28th, 2009, 09:39 PM
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I really think the new doors are pretty well treated. As long as you keep some waxoyl in them they out to be great. The galvanic corrosion problem from the ali skinned ones is solved, so just keep the drains open and the frames well-lubed and you should be good for a very long time.
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  #12  
Old November 2nd, 2009, 09:50 AM
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Yeah, really bad idea. What you probably want to do is run seam-sealer around all the corners to make sure moisture cannot sit in place. If I was really paranoid (which I am) one option would be to make the door inside accessible for drying, say a couple removable bung plugs which would then let you use something like a hair-dryer to make sure any moisture is gone. (though just having a way to open them to dry air would probably help a lot). Something that would also let you rinse the inside of the door to remove any accumulated salt would also work.

Personally though, with the galvanized all steel door, repairs are possible vs next to impossible with the previous type of door (without new skins) so I am not as worried.
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  #13  
Old November 2nd, 2009, 10:24 AM
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Use POR-15. If you need to take the skins off to do a complete treatment, that's the best way to go.
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  #14  
Old November 2nd, 2009, 10:36 AM
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If you are going to POR-15 you will also need to sandblast it to get enough grip for it to stick. I would rather use a rubberized product like a latex sealing compound, or something like the VB1x from Cascade Audio Engineering which will stay flexible. I am probably going to just line the insides with B-Quite Ultimate where I can get to it easily, and pour something like VB1x along the bottom where I cannot, the main thing though is to make sure they are going to drain properly so don't block the drain holes in the process.
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  #15  
Old November 2nd, 2009, 12:24 PM
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Actually, POR-15 does not recommend blasting before applying the product You must degrease with Marine Clean, apply Metal-Ready, allow to dry and then paint with POR-15. The product requires a somewhat rusty surface to adhere properly. Once cured you cannot even hammer it off. Long time customer and I swear by this product for both auto and marine use.
I'm about to repaint my Brush Bandit Chipper and will use POR-15 products exclusively.
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  #16  
Old November 2nd, 2009, 03:31 PM
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I POR15 my ST doors and have been very happy, they have held up very well.
I just followed all the instuctions & it bonded to the frames and skin.
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  #17  
Old November 3rd, 2009, 10:09 PM
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Cold galvanizing spray would be another option, it is mostly zinc
and would be sacrificial as well as a coating.
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  #18  
Old November 3rd, 2009, 11:43 PM
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Why are Rover owners so damn crazy about galvanizing everything? It's wierd.

I'm waiting for one of you guys to try to teabag your balls in a galvy tank.
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  #19  
Old November 4th, 2009, 12:37 AM
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Maybe due to the fact that the manufacturer does such a poor job with corrosion prevention from the factory?

You would think that a company from England would be the experts on keeping water out and corrosion prevention but they seem to be unaware of how to properly coat metal.

Every time I see someone post pictures of a rusted out salt lick of a Defender I thank my lucky stars that I live in Colorado.
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  #20  
Old November 4th, 2009, 06:55 AM
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They're into galvanizing because Rover was onto something when they riveted bare aluminum panels to galvanized steel back in the 40's. Unfortunately they got away from that and now everything rusts. Here is info from an architectural structure design firm:

1. Theory predicts that Aluminum and galvanized steel are compatible. These materials are adjacent to each other in the galvanic scale (e.g. Jones [1], pg. 169). The presence of aluminum coupled to the galvanized steel increases the current density (corrosion rate) of the zinc by only 0.1% to 1% (aluminum is the cathode, or protected side of the couple) (Jones [1], table 6.17, pg 184). This increase in the corrosion rate of zinc is negligible, and therefore, the contact between the aluminum and galvanized steel does not accelerate significantly the corrosion of either material.

2. Testing confirms the theory. For example, Doyle and Wright [2] show that the rate of corrosion of aluminum does not increase from being in contact with galvanized steel. They conclude: "zinc is very compatible with aluminum in all atmospheres, in several cases showing that aluminum was actually cathodically protected by zinc.

3. Codes have incorporated the above results. For example, the Aluminum Association in its structural code states that there is no need to separate or paint galvanized steel surfaces in contact with aluminum. (Aluminum Design Manual [3], pg. I-B-62).

4. Many structures and components by Geometrica and others built over the past half century attest to the above. Aluminum cladding is frequently fixed to galvanized structures, and often using zinc coated fasteners. Most exterior grandstand structures in North America have galvanized understructure to which structural aluminum seating and flooring is fixed. And countless Geometrica hubs in service around the world join galvanized steel tubes successfully and permanently.

[1] Jones, D., Principles and Prevention of Corrosion, Mcmillan, New York, 1992.
[2] Doyle, D.P. and Wright, T. E., "Quantitative Assessment of Atmospheric Galvanic Corrosion", Galvanic Corrosion, ASTM STP 978, H.P.Hack, Ed., American Society for Testing and Materials, Philadelphia, 1988, pg. 168.
[3] Aluminum Design Manual, The Aluminum Association, Washington D.C., 2000

Source: http://www.geometrica.com/steel-or-aluminum

Follow-up Post:

And my galvanizer wouldn't let me try the teabag thing, turn out their tank wasn't big enough
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