I still want to know why replaceable “Boat Zinks” are not used on automobile undercarriages.

I guess I ought to know,
as I have taken two graduate level courses on Corrosion,
but I admit I do not know why.

Best part of those corrosion courses was the field trips to the
LaQue Corrosion Center on Kure Beach NC,
with its hundreds of racks exposing different metal alloys to the salt air,
and down just barely back from the beach, dozens of air conditioning condensing units being evaluated in such harsh conditions under contract.
Then the course Professor would take us off shore fishing.

https://www.starnewsonline.com/article/NC/20040220/News/605083433/WM

For WW-II history buffs
The LaQue field test center sat on the island site of the rapidly built plant to extract Magnesium and Bromine from seawater
so that the USA could produce the lighter/stronger aluminum alloy
that was one of many reasons the Mitsubishi Zero naval fighter
could climb so fast and have such long range.
Irony here: Howard Hughes used Al-Mg alloys in his HR-1 racing airplane
and Japanese espionage stole many of Hughes innovations,
then signed a licensing agreement to build Curtis Wright engines in Japan.

After WW-II Canadian owned International Nickel Company bought both the plant and all Kure Beach island at a war surplus auction for 10% of what it cost to build.
Plant manager Francis LaQue later became President of International Nickel.