Strange corrosion

[L124C]

I'm looking at a Islander 30 fixer. Both flush mount bow nav light housings show heavy corrosion that I've never seen on anything that hasn't been submerged. The boat needs work, but I don't see any other signs that it was sunk. This is the only metal on the boat that looks like this. Thoughts?

Completely unrelated, but, it just occurred to me....shouldn't another boat be able to see both lights when directly off the bow ( at 12 o'clock)? Seems to me that since the lights are recessed in the hull, another vessel couldn't see either! How does that work?

[celenoglu]

This type of corrosion is not rare. But the metal is not fit for marine use.

The lights can be seen from 12:00 if you are far enough.

[Maine Sail]

Originally Posted by L124C

I'm looking at a Islander 30 fixer. Both flush mount bow nav light housings show heavy corrosion that I've never seen on anything that hasn't been submerged. The boat needs work, but I don't see any other signs that it was sunk. This is the only metal on the boat that looks like this. Thoughts?

Completely unrelated, but, it just occurred to me....shouldn't another boat be able to see both lights when directly off the bow ( at 12 o'clock)? Seems to me that since the lights are recessed in the hull, another vessel couldn't see either! How does that work?

Most likely older Perko chrome plated zinc alloy... One of the dumbest ideas to ever hit boating...

[TQA]

The tops of my 70s Barients self tailors look like that.

[RichH]

The corrosion is zinc oxide which is 'extracting' from a poured casting of *pot metal* or *white metal* an inexpensive and dubious alloy of mostly zinc and varying % of tin, aluminum, magnesium, lead, etc. In the foundry trade this was also called *monkey metal*. This is a very weak alloy which quickly corrodes in the presence of water, especially seawater even if plated with nickel or chrome.

[L124C]

Originally Posted by celenoglu

This type of corrosion is not rare. But the metal is not fit for marine use.
Ain't that the truth!
The lights can be seen from 12:00 if you are far enough.

I wonder how, since the hull and light fixture itself seem to be in the way. In any case, it's the close boats I'm worried about!

[RichH]

These hull mounted 'eyeball type' navigation lights were deemed 'inefficient for visibility and safety' by the worlds marine community ... in about ~1967(?). And by universal agreement (ABYC, SOLAS, ABCDEFG, etc. etc.) none were installed on recreational, etc. boats after that time.