Creative use of zinc anodes question?

pateco

pateco

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Aug 12, 2014
2,207
Hunter 31 (1983) Pompano Beach FL
I posted this In Maine Sail's forum last week, and no one has replied, so I am posting it here as well.

I have a non boating related question regarding the use of zinc anodes. I know on our boats that the zinc anodes help prevent corrosion of the steel parts. I'm in the midst of redesigning a satellite television distribution system for a high-rise Building located directly on the beach. The existing system was installed in powder coated Steel boxes. With all of the salt from the ocean these boxes have rusted to pieces in a very short period of time. They are 24x24x11 locking low voltage distribution boxes, and I can't find anything that will do the job in plastic for a price that works. I was wondering if I rebuild using the same style new boxes but add zinc anodes to them do you think the zincs will prevent the boxes from corroding? The boxes look like this.

View attachment 123353
 
Don S/V ILLusion

Don S/V ILLusion

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Sep 25, 2008
7,688
Alden 50 Sarasota, Florida
My chemical engineer training tells us it won't work for the following reason. A boat's anode essentially creates a battery diverting stray current causing erosion away from the protected metal. In the ambient environment, in broad terms, it isn't stray current which causes your problem but rather oxidation for which any anode would offer little protection.

Your best option is to find some non-ferrous metal enclosures.
 
C

Capt jgw

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Feb 8, 2014
1,300
Columbia 36 Muskegon
I doubt zinc would help. Zincs work when two different metals are immersed in an electrolyte, like salt water. The zinc leaches away instead of the metal you're protecting. Unless the box is under water, there won't be an electrolyte. If the box was completely coated in zinc (galvanized), that would work, but only until the first scratch through the coating appears. Then the rust starts. Plastic may be your only option, it's what we get for wanting to be near the ocean. Salt air and steel just don't get along together.
 
rgranger

rgranger

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Jan 19, 2010
12,926
Hobie 16 & Rhodes 22 Skeeter Charleston
Not the way you describe but .... sacrificial zinc electrodes are used to protect underground steel tanks, and well pipe. You would need to put the zinc in the ground and connect it to the box with a grounding strap.

Here is a website for more info

http://www.cathodicme.com/sacp.html
 
Charles Erwin

Charles Erwin

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Jan 30, 2012
1,154
Nor'Sea 27 "Kiwanda" Portland/ Anacortes
Zincs (also called anodes) are used to prevent galvanic corrosion. Galvanic corrosion occurs when dissimilar metals are electrically connected (a manganese bronze propeller bolted to a stainless steel shaft) and submerged in an electrolyte. In the case of a boat the electrolyte is the water and the metal with the lower electrical potential wastes away in a reaction with the metal of the higher potential. Fastening a zinc onto the propeller assembly results in the zinc wasting - it has a low electrical potential - rather than the manganese bronze propeller. Galvanic reactions occur even if one of the metals is not iron. Anodes can also used to prevent galvanic corrosion of other structures immersed in an electrolyte - like buried pipelines and piling.

The corrosion you describe is not a strictly a galvanic (electrical) reaction rather it is oxidation between iron and oxygen in the air. To illustrate - your car body is made of steel and is subject to the same elements as these junction boxes - but your car is not rusting. Your car has no zincs but it has very good coatings.

In short - anodes will not prevent the corrosion you describe.
 
agprice22

agprice22

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Aug 3, 2012
2,542
Performance Cruising Telstar 28 302 Watkins Glen
Why not create the boxes you want from scratch using HDPE or PVC sheets? You can weld these materials with heat or glue very quickly. The materials are essentially impervious to the elements.
 
Gunni

Gunni

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Mar 16, 2010
5,937
Beneteau 411 Oceanis Annapolis
Talk to a corrosion engineer, they use impressed current to thwart corrosion on metals in contact with earth.
 
C

Cayennita

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Nov 28, 2009
495
Catalina 30 St. Croix
agprice22 said:
Why not create the boxes you want from scratch using HDPE or PVC sheets? You can weld these materials with heat or glue very quickly. The materials are essentially impervious to the elements.
Click to expand
Agprice22 has the right answer. Use a non metal material abd build the boxes. Homedepot has plastic garden storage boxes, both upright and horizontal. Many different sizes.
 
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