repair hot dipped galvanizing


After a reapair I have and area where I machined off the galvanizing
on a hot dipped piece of steel. I have some zinc and I was wondering
if there was a way I could apply the zinc rod sort of lie soldering to
repair the damaged galvanized coating. In the past we have sprayed the
area with cold- gal and this has not been satifactory.
Jimmie
Reply to
JIMMIE
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rmcdemus had written this in response to
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:
Bob McDemus
Hi Jimmie:
This is a common request that has been cropping up for people doing repair and construction in the field for things like Wind Mill towers. The Navy addressed it years ago by going to a Thermal Spray Process, sometimes called spray welding, for applications on the ships. Basically you take a heat source, melt zinc or aluminum, atomize it, then spray it. It basically is hot dip galvanizing that you can do on site. To see the thermal spray equipment and some video's of the process, go to
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and look at the web site.
A second web site that you can look at is
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There is a summary available there of a 19 year corrosion test that was done by the American Welding Society (AWS) on thermal spray coatings.
Hope that helps
Bob McDemus ------------------------------------- JIMMIE wrote:
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Reply to
rmcdemus
We use a lot of hot-dip for projects at the Dive School.
I have always had good luck repairing the zinc with Cold Galvanizing spray. The can should be really heavy or it isn't worth spraying.
In article , JIMMIE wrote:
Reply to
Ernie Leimkuhler
The Crown 7008 Cold Galvanizing Compound I brushed onto repairs on my pickup truck didn't hold paint and is about half covered with rust color.
jsw
Reply to
Jim Wilkins
I used a Spray can. Got mine at Home Depot. The larger than normal can was a heavy one.
I zincked my large outdoor vise then painted it bronze over the zinc.
I have always heard that if you have zinc plating on anything - paint it. It will last many more years if done.
I have zinc plated fence line that is rusting top down. Zinc flows and it dissolves with acidic rain - e.g. tree leaves drip acidic rain. An example are oaks. Tanic acid. Redwood more Tanic acid....
Martin
Jim Wilk>> We use a lot of hot-dip for projects at the Dive School.
Reply to
Martin H. Eastburn
...
LPS3 protects the galvanized steel roofing on my woodshed from oak leaf tannic acid pretty well. I thin it at least 50% with kerosine and spray with their pump spray bottle. A light coating lasts at least a year. The plating on the Home Depot and lowe's corrugated panels is thin enough that I've bought some (discounted) that already had corrosion and rust spots from trapped water.
jsw
Reply to
Jim Wilkins
The way zinc on steel works to protect the steel is the zinc is sacrificial. As long as there is zinc in the area of the water droplet where the corrosion is occurring the steel in that area won't corrode until all the zinc is gone. This is the opposite of chrome where if you get a pit in the chrome the corrosion occurs faster in the pit. more layers of paint may well keep the corrosion in general down but as for protecting a defect in the coating painting over galvanizing would seem not to be sensible. I can assure the zincs on steel fishing boats under the water line aren't painted but the hull is. Now whether there is really an electrical connection with the paint on zinc I can't say.
Fran
Reply to
fran...123
Exactly right. Zinc will work to protect the steel, but it won't last forever.
On boats the hull is painted but the welded-on studs are not. The studs provide an electrical connection (grounding) between the zinc and the steel hull. If you do not have that connection, or if the zinc gets painted, there won't be much if any electrolysis of the zinc, leading to corrosion of the steel.
Once the zinc in attached securely (typically with Nylock nuts and split washers) you can paint the studs, but you still must leave the zinc bare to allow the electrolysis to occur.
Reply to
TinLizziedl
Zinc on boats is another story altogether.
I do posts and such. Boats have are riding on an electrolyte and the motor and boat both cause corrosion with each other. Thus the sacrificial magnesium rods.
Martin
T> >>> I used a Spray can. Got mine at Home Depot.
Reply to
Martin H. Eastburn

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