chrome plating on bronze parts

[markxengineerin]

I have a couple of these:

and want to use as a replacement for


The toggle is installed between a stainless steel chainplate and a stainless steel eye fitting on head stay.

Is the chrome coating commonly found on bronze rigging parts strictly a cosmetic thing, or is it significant for preventing corrosion? This assembly is on deck- frequently splashed w/ salt water but not submerged.

Alexander Roberts aka Arco does not know: "We do not manufacture these, we import them, did you ask a rigger?" Interestingly, I got a similar answer a few weeks ago when I contacted Hayn about strength of their parts. These companies can not/will not provide any information besides dimensions, and it's the rigger's job to determine what's safe and what's not. Strange industry.

[tkeithlu]

The corrosion on bronze actually helps protect the underlying metal and is not significant in terms of strength. Plating it doesn't really change the situation.

Bronze and stainless steel have about the same tensile strength, so inserting that bronze fitting in a stainless steel rigging sequence is OK, if unusual. The major difference is that when you get close to failure the bronze will elongate while the stainless steel will fracture suddenly.

[s/v Jedi]

Originally Posted by tkeithlu

The corrosion on bronze actually helps protect the underlying metal and is not significant in terms of strength. Plating it doesn't really change the situation. However, a bronze fitting like that one will not be as strong as a stainless steel fitting with the same dimensions. It seems a bit odd that someone would insert a bronze fitting, plated with chromium or not, in a sequence of stainless rigging.

The bodies of my turnbuckles are chromed bronze too. I think this is done mostly to prevent galling with the stainless steel stud threads, but it’s just bronze taking the load.

[tkeithlu]

I had editied my post because the tensile strength of bronze is a lot closer to the tensile strength of stainless steel than I thought. The big difference between the two is ductility, ergo stretch before breaking.

[markxengineerin]

bodies of my turnbuckles are chromed bronze too

Yes, I'd feel better about it if someone has an example of un-chromed bronze mechanically touching stainless steel for a long period of time, on deck, without corrosion. We have all seen what stainless does to aluminum, but there seem to be fewer examples of stainless+bronze. At least I haven't come across any in my very limited experience.

[Dave_S]

I agree with tkeithlu.

and

They use bronze bushes for stainless steel prop shafts in fresh and salt water.

[Orion Jim]

Originally Posted by markxengineerin

Yes, I'd feel better about it if someone has an example of un-chromed bronze mechanically touching stainless steel for a long period of time, on deck, without corrosion. We have all seen what stainless does to aluminum, but there seem to be fewer examples of stainless+bronze. At least I haven't come across any in my very limited experience.

My bronze turnbuckle bodies have spent the last 38 years touching stainless steel. Galling has never been an issue. When I replaced my standing rigging I went with Sta Lok threaded end fittings and studs. I retained my original bronze turnbuckle bodies as they are all in as-new condition.

[Manateeman]

The pin in the toggle. Is IT going through the chainplate? Is the toggle pin down like the photos? How are you connecting to the rigging? Jaw / jaw turnbuckle?
We’ve had 1/2 inch pin bronze toggles at the lower end of a bobstay into a stainless cross pin between two bronze plates for 30+ years on a boat I built long ago. The toggles are in and out of the salt water because they are right above the waterline and I don’t see any elongation or looseness in the pin hole in the bronze. I think the toggles were Merriman.
There is bronze and there is junk bronze metal. Same with stainless.
The Merriman has a little Neptune fork on it.
We don’t give rigging advice online.
The manatees

[thinwater]

Originally Posted by markxengineerin

Yes, I'd feel better about it if someone has an example of un-chromed bronze mechanically touching stainless steel for a long period of time, on deck, without corrosion. We have all seen what stainless does to aluminum, but there seem to be fewer examples of stainless+bronze. At least I haven't come across any in my very limited experience.

The threads inside the turnbuckle are not plated. That is kind of the whole reason they are bronze (galling).

[s/v Jedi]

I think the only reason for chrome plating the bronze parts is to keep the green copper oxide out of sight. You can order the same turnbuckles without the chrome which is what is preferred for traditional yachts and they look great I think. Better than failing chrome plating when aging.

[Manateeman]

So true. Listen to the Jedi Master. He knows what he’s talking about. Getting bad chrome off bronze is nothing like off steel. Not a hot rod job shop item. We had a winch we wanted the chrome off and it was new. The results were great but the guy who did the job really was skilled. Just some chunk of bronze like a cleat, is easier but anything rigging?? We’d pass on touching it.
So are the toggles Merriman?
Mark

[markxengineerin]

Thanks to all for the advice- I am proceeding as planned, with one less thing to worry about. I believe the orientation will be like we are looking at in photos, and all the parts involved are from what seem to be reputable brands. Gibb, hayn, and arco.