My Sacrificial Anode in my wate tank seems to be working

[gimmeagig]

Hi guys,
I posted earlier about trying to protect my waste tank in my aging CDS from any more leaks. I heard that if I put a block of zinc into the tank and run a grounding wire to it it would act as a sacrificial anode and the chemicals would eat away at the block of zinc instead of my tank bottom.
Someone else said that zinc is the wrong material because it will only work in salt water.
I don't have a lot of money and I would hate to have to replace the tank. So I decided to give it a try anyway and bought an anode sesigned for boats at a marine supply place. I ran a wire to it and drilled a hole in a inside panel in my tank to ground it. It has been in there now for about 4 months and I just pulled out the anode to see if there is any change.
Here are the pictures:

This one was the dirty anode.As you can see there is some type of slime on there

Here's another shot of it.

This is the anode after I cleaned it off. As you can see there is a deterioration. So it seems to be working.

This is the bottom of my tank where the anode used to be.There is this yellowish epoxy like stuff that stuck to the area around where the anode was located. I am not a chemist and I'm wondering if anybody here can tell me what that might be and if it is indeed working.
It really does seem to be doing something I just don't know what exactly it is that it is doing and what the byproducts of this chemical reaction are.I'm not sure if it is eating the anode instead of my tank (I sure hope so)or if my tank is still in jeopardy. I'm also wondering if there are any tabs that I could drop into the tank to protect it.
So for all the scientifically incline people here.
What do you think about this?

 

[Mikey P]

in the words of Ron Lippold..
WOW!

 

[sweendogg]

From a Physics major's stand point.

The science is sound. The zinc is more reactive than aluminium and this is more willing to give up an electrons and attract the oxidiation that aluminium Thus keeping your waste tank cleaner.

here is an excerpt from Wikipedia that gives you the technical jargain.

Anti-corrosion and batteries
Hot-dip handrail galvanized crystalline surfaceThe metal is most commonly used as an anti-corrosion agent.[91] Galvanization, which is the coating of iron or steel to protect the metals against corrosion, is the most familiar form of using zinc in this way. In 2006 in the United States, 56% or 773 thousand tonnes of the zinc metal was used for galvanization,[92] while worldwide 47% was used for this purpose.[93]

Zinc is more reactive than iron or steel and thus will attract almost all local oxidation until it completely corrodes away.[94] A protective surface layer of oxide and carbonate (Zn5(OH)6(CO3)2) forms as the zinc corrodes.[95] This protection lasts even after the zinc layer is scratched but degrades through time as the zinc corrodes away.[95] The zinc is applied electrochemically or as molten zinc by hot-dip galvanizing or spraying. Galvanization is used on chain-link fencing, guard rails, suspension bridges, lightposts, metal roofs, heat exchangers, and car bodies.[10]

The relative reactivity of zinc and its ability to attract oxidation to itself makes it an efficient sacrificial anode in cathodic protection (CP). For example, cathodic protection of a buried pipeline can be achieved by connecting anodes made from zinc to the pipe.[95] Zinc acts as the anode (negative terminus) by slowly corroding away as it passes electric current to the steel pipeline.[95][note 2] Zinc is also used to cathodically protect metals that are exposed to sea water from corrosion.[96] A zinc disc attached to a ship's iron rudder will slowly corrode while the rudder stays unattacked.[94] Other similar uses include a plug of zinc attached to a propeller or the metal protective guard for the keel of the ship.

With a standard electrode potential (SEP) of ?0.76 volts, zinc is used as an anode material for batteries. (More reactive lithium (SEP ?3.04 V) is used for anodes in lithium batteries ). Powdered zinc is used in this way in alkaline batteries and sheets of zinc metal form the cases for and act as anodes in zinc–carbon batteries.[97][98] Zinc is used as the anode or fuel of the zinc-air battery/fuel cell.