Non-Magnetic Chrome Plating

[SVTatia]

I have to restore my binnacle compass housing and I would like to know if anyone can recommend a place that uses non-magnetic plating. I am unable to find such a process in my area. Thanks.

[mike d.]

Chrome plating should not be magnetic, I believe! The base metal should brass, or bronze ! This usually gets a coating of copper, then chrome, at least that's the way plating was when I had it done in the 70s

[Jim Cate]

Top quality chrome plating on steel utilizes first copper, then nickel and then finally the chrome. None of these are magnetic. You haven't told us w hat the base metal is in your binnacle, but I would imagine brass or bronze. In that case, proper plating would involve only the Ni and Cr layers.

I think there is some misunderstanding here...

Jim

[SVTatia]

Thank you all for responding.

Well, I have never related chrome plating to magnetism, but then I read this article from which I paste the following excerpt:

"...The compass was disassembled and the housing shipped to Circle Polishing in Newburyport, MA. Circle Polishing does all the restoration chrome for Ritchie Navigation and has a proprietary process for non-magnetic chrome (as opposed to more typical industrial hard chrome processes)..."

I called a few local shops and asked whether their chrome process is magnetic - after the initial surprise and few seconds of silence they mentioned that it is...

I called Circle Polishing and they confirmed their process, but shipping and the cross border issues would make it a costly job.

Now, if you are all correct, which I am sure you are, how do I verify that the compass will not be affected before having the work done?

BTW, looks like the compass housing is made of brass.

Here is the Bonne Amie restoration article I mentioned:

*The Bonne Amie Chronicles: E. S. Ritchie Globemaster Compass Restoration - Part I

This is my compass housing:

[Jim Cate]

Very interesting! I'm at a loss to understand where the magnetism is supposed to come from, though. The veiled reference to "hard chrome processes" may be a clue. IIRC, hard chroming is used to improve surface hardness on things like crankshaft bearing journals and cylinder bores. It has little relationship to decorative chrome plating such as is on those beautiful compass housings.

At any rate, I await with interest someone explaining this conundrum. BTW, our Ritchie compass has a polished stainless housing. I wonder how they avoid the minor magnetic effects made in 300 series stainless when it is cold worked (as in polishing)? Perhaps annealing after polishing?

Jim

[UNCIVILIZED]

Jim, to remove most of the magnetisim after polishing, might something akin to degaussing work? It's commonly done to large military ships to reduce their magnetic signature. https://en.wikipedia.org/wiki/Degaussing

The other thing though is that compasses should regularly be swung, so that the amount of error in them is known. Particularly since the earth's magnetic field varies from location to location. Including in regions where there are large concentrations of magnetic, or ferrous rocks/ore.

Albeit most of this is probably moot should you just switch to a flux gate, or gyro compass

[Jim Cate]

Originally Posted by UNCIVILIZED

Jim, to remove most of the magnetisim after polishing, might something akin to degaussing work? It's commonly done to large military ships to reduce their magnetic signature. https://en.wikipedia.org/wiki/Degaussing

The other thing though is that compasses should regularly be swung, so that the amount of error in them is known. Particularly since the earth's magnetic field varies from location to location. Including in regions where there are large concentrations of magnetic, or ferrous rocks/ore.

Albeit most of this is probably moot should you just switch to a flux gate, or gyro compass

Yes, degaussing would work, and is probably what is done if required.

Just to pick a nit with you, swinging one's compass does nothing to deal with shifts in the earths magnetic field (variation), only with changes in the ship's own magnetic field (deviation). And flux gates are subject to these changes as well, but usually have software enabled corrections built in, activated by doing the boring slow speed circles, far easier that conventional swinging.

And I still wonder about magnetic chrome!

Jim

[UNCIVILIZED]

Might the chrome be slightly magentic due to some of the chemicals & process when applying it being magnetic? That, or perhaps it's that so many of the other items being chromed are ferrous that a bit of this material gets transferred to the agents used in chroming, & are thus deposited on the compass housing when plating it.


And, yep, I know the truth about swinging compasses. But thought it worth mentioning.

[Eigenvector]

So this thread peaked my interest to the point that I spent a couple hours trying to find out why.

A nickel substrate layer is laid down first which acts as a "self leveling" layer to improve the finish of the subsequent chrome layer. The nickel layer will be magnetized in the conventional application methods. To alleviate this, electroless nickel plating is utilized as the substrate layer.

[SVTatia]

Originally Posted by Eigenvector

So this thread peaked my interest to the point that I spent a couple hours trying to find out why.

A nickel substrate layer is laid down first which acts as a "self leveling" layer to improve the finish of the subsequent chrome layer. The nickel layer will be magnetized in the conventional application methods. To alleviate this, electroless nickel plating is utilized as the substrate layer.

Thank you Eigenvector.... electroless is also something new to me.

I called around and found a local plating shop that also does electroless, I'll be seeing them next week and I'll take my compass to test it around their plated jobs. He mentioned that electroless would be okay, by it is not a cosmetic finish, it is very dull... He also said I am thinking too much about the regular chrome plating... I'll bet he is right...

Thanks for the interest and I'll keep you all posted.

[mike d.]

Well you learn something new every day ! The shop in Newburyport is quite good I use/d them for re-anodizing my mast step base, a few other things ! They are local to me ! Nice people to deal with !