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wire wheel retaining ring heat treatment after chroming


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I am in the process of having wire wheels retaining rings triple chrome.

I was told by another restorer , heat treatment is needed after chroming to prevent cracking.

I did a little research and it was noted to do heat treatment to 300 degrees for 3 hours then air cool,

This will take out hydrogen embrittlement, Article mention to do heat treatment between coat of copper,nickel and chrome.

Has anyone had problem with rings cracking after chroming?


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The guy who did my body work said he's seen a radiator fan that was chrome plated crack and went through the side of the bonnet. There are a few pieces on my car that needed to be heat treated. For $20 it's cheap insurance. Especially for rims where stress is applied.

If it was me I wouldn't hesitate.

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My cooling fan was cracked at one stage too. They do a lot of work and I expect it was plain old fatigue. Mine was painted. Anyway, I doubt that fan blades are high strength steel.


The article referred to above appears to relate to hard chrome, which will provide a wearing surface. Triple plating - Cu, Ni, Cr - is not mentioned. So one needs to ask about copper plating first. Copper is put on for two reasons: to fill roughness (which can then be polished out) and to provide a non-porous surface on which to put the Ni and Cr, both of which are porous.


The question then arises, if hydrogen is deposited into the pores in the crystal structure during copper plating, how will it come out when the article is heated if the coating is non-porous?


The other question concerns what the locking rings are made of. Are they high strength steel? Are they some grade of spring steel? Are they particularly susceptible to hydrogen embrittlement?


This is not a simple one-line-answer question!



Wikipedia says this:

"Steel with an ultimate tensile strength of less than 1000 MPa (~145,000 psi) or hardness of less than 30 HRC is not generally considered susceptible to hydrogen embrittlement." 


Our rings are not near that strength!

Edited by Spinneyhill (see edit history)
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I have the ovens , and they will call me as soon as I can pickup, I will do heat treatment, my only problem is I will not do between platings, , he is doing nickel, nickel, chrome, no copper. The only thing he says don't get it to hot because it will blister chome.

I am planning on 180 for 3 hours. Only.

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All steel parts having a hardness of Rockwell C40 (180,000 PSI) and higher must be baked at 375 degrees F, plus or minus 25 degrees F for 3 hours minimum after plating to release hydrogen embrittlement.  I would suggest if you don't know the hardness of your parts being plated you can safely bake them in a home oven. Preheat your oven to 375 F then put your plated parts in. The plating should not blister if the electro-plating process was done correctly. Plated parts do not have to baked in between plating steps but I would recommend them being baked within 24 to 48 hours after plating.  In the Industry, Auto, Areo and the like most materials designed for decorative plating ( Cu. Ni. Cr. ) are of materials that don't need hydrogen embrittlement release. 

Edited by Old School Plating (see edit history)
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Thanks for the advise old school plating.

I will be using a oven , but not the one in house, The wife would not appreciate that.

I have a professional oven at the aircraft shop, has controls and timers for doing it on control temp and times.

I don't figure it really needs it for soft chrome, but why take a chance,

Will keep the peace at home,

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  • 5 weeks later...

The hydrogen comes from the acid used in plating, now you are down to time (more exposure is worse) and hardness.  If the steel is not hard enough the hydrogen will not permeate the carbon (what makes steel hard), soft steel will not have enough carbon to get hydrogen embrittlement.  So you bake the steel to let the hydrogen molecules out (the heat excites the atoms and out goes the hydrogen) you would need to bake the steel soon, within a couple days to release the hydrogen otherwise its stuck.


My guess is another likely problem, work hardening, after 80 years that is a lot of stress...


I would also guess a flat tire sitting in one spot might cause some stress?


I have not checked the hardness on my rings, but I always thought they were hard steel?

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