Aluminum Heads Corrosion Protection

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For those with aluminum heads, or maybe an aluminum radiator or other replacement parts in their car’s cooling system: the latest catalog from Snyder’s Ford Parts on page A-117 offers a “head saver” Item A-6010 AHS, which is an anode of magnesium or zinc which is intended to be placed in the coolant; very well-known and effective protection used for many years, and an easy  price of $6.95.

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Anodes are an an old and interesting idea; at one time, they are an accessory sold at parts store. I still have one in my car while sorting out its water pump issues.  While not a replacement for an anti-corrosion fluid, but it is a pretty good temporary solution while you are tracking down cooling system problems.  Any two different metals connected by an electrolyte forms a battery; such as the old Lead/acid batteries, which lead and lead oxide, having different electrical potentials. Chemistry behind the sacrificial anode is to use a more active metal than anything else in the system. Any two different metal compounds connected by an electrolyte forms a battery; such as the old Lead-acid batteries, using lead and lead oxide, having different electrical potentials. The two common anode materials are zinc and magnesium. My strong preference is zinc, because magnesium burns if it gets too hot during fabrication.

The “normal” configuration of our cars is a cast iron engine and a copper radiator. Iron and Copper also form a battery with current flow between the metals when submerged in a conductive fluid. Unfortunately, iron is the more active and sacrifices itself, forming red iron oxide (hematite), minimizing oxidation in the radiator. The good news is that zinc is more active than both copper or iron, so the zinc oxidizes to protect the block and radiator. Some anodes are available to bolt into the block, but these require draining the cooling system for installation. My preference is to place the anode in the radiator’s top tank and electrically bond it to the radiator neck.

The anode I made is a section of 1/2 inch zinc rod about 1-1/2 inches long. This is small enough to fit  through the neck, turn and lay on the bottom of the upper tank, which is by far the most accessible point on the cooling system. Zinc is a soft metal, so I have a copper wire screwed to one end. The other end of the wire is stripped and pinched between the neck and radiator cap, completing the circuit. The wire is also good for pulling the anode out to see its condition; does it needs to be replaced or have excess oxidation removed?

Rods of pure zinc, 1/2 inch diameter are available. The site <span style=”text-decoration: underline;”>boatzincs.com</span> sells such as a rod 1/2 diameter x 36″ long for about $23. This much zinc is more than a lifetime supply by cutting off what you need at the time.  Still, it is a temporary solution if the cooling system is being drained frequently and must be submerged into the cooling water to function. Anodes are not a substitute for commercial anti-corrosion fluids, but they can be used together.    Herb

 

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Herb, a friend who has operated a boat repair facility for years insists on magnesium anodes for boats to be operated in fresh water, and zinc anodes for those operated in salt water.  West Marine’s website provides the same guidance.  Can you clarify why zinc, rather than aluminum, should be used in automotive cooling systems?

By the way, pre-1921 Pierce cooling systems have quite the mix of dissimilar metals:  iron blocks, copper radiators, bronze water pumps, brass distribution tubes, and cast aluminum water manifolds carrying hot coolant to the radiator.  From experience, the cast aluminum becomes the sacrificial metal in these cars.

George

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George, you are correct on both counts. Zinc is more active than aluminum and many parts of outboard motors are made of aluminum.  On the other hand, while zinc protects the aluminum heads and other aluminum parts in a cooling system, it does not really help with other metals in the engines of our cars.

After reviewing the Periodic Table, the Magnesium is indeed a more active metal than either iron or copper, so I agree with your friend that magnesium is better as it would help protect engine blocks and radiators (plus other copper alloys such as brass and bronze).

Two reasons I chose zinc: I remember back in the day that makers of mag wheels had a distinct fire hazards due to the magnesium being igniting from their machining processes and burning very hot. Secondly, zinc is more readily available in a form that could easily be made to fit into the radiator neck.

Now that the water pump and hoses are nearly sorted out, I am going to put in liquid anti-corrosion fluid when finished. Pump is OK, but the hose wall is too heavy for the correct clamps to seal properly. One last drain and refill to change out the hoses from pump discharge to the radiator should take care of it.

Thanks for asking about my posting – I should have checked my chemistry more closely. Apologies. Herb

 

 

 

 

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Herb, no apology necessary; we’re all exchanging ideas here.  Marine stores such as West Marine have pre-made magnesium and zinc anodes in various sizes and shapes.  My 1918 came with a probably-zinc anode in place in the top tank:  a cylinder about 3/4″ diameter and now about 2.5″ long, drilled axially with stainless wire through it, the end of which is formed into a hook similar to that on a Christmas tree ornament, slipped into the overflow tube and gently compressed against the tube to keep it in place.  The anode rests on top of the radiator core.

Suggestion for your rad hose installation:  In my experience, authentic clamps never seal new hoses properly, especially on cast iron.  I’ve learned to put a pair of authentic clamps in the middle of each run of new hose, tightened just enough to prevent them from flopping around, then use modern worm gear type clamps for the initial installation–and leave them on for 20-30 heating-cooling cycles until the hose has had an opportunity to “bond” with the cast iron.  If you have a lot of pitting on the cast iron mating surfaces, JB Weld smoothed and sanded will help.  After a number of heating-cooling cycles, remove one modern clamp at a time, “breaking its circle,” and slide the corresponding authentic clamp into position.  I’ve rarely been able to refit an authentic clamp once I’ve “broken its circle.”

For the radiator outlet to water pump hose run, I prefer have short lengths of straight hose (about 4″ of unsupported length) on each side of tubing to which a drain valve has been affixed.

What anti-corrosion fluid are you using?  I’ve been using Pencool (formerly Nalcool) for years but have found on my 1918 that a too-rich mixture causes seepage and Pencool’s purple stain–which may mean that it’s attacking the solder.  A leaner mixture for topoffs seems to reduce this effect.

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