Chroming Parts

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Kyle Boatright

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The RV-10 has 4 unique hinges for the doors. They are plain 'ol steel and are partially exposed to the elements. I'm tempted to have them chrome plated to avoid the chipping/rust that (I think) would happen due to the relative motion of the hinge halves if I painted the hinges.

On the other hand, I've read about hydrogen embrittlement, but don't really understand it. What I wouldn't want to do is create a structural problem in the hinges with the plating process - the hinges are part of a fairly weak door attachment system and I don't want any of them to crack/break.

So, what questions do I ask at a chrome plating shop to make sure they know what they are doing and to avoid hydrogen embrittlement?
 

BBerson

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I took a Cherokee nose wheel strut to a chrome shop. Got a call back and the shop said the steel tube strut cracked while they were rechroming it. He said they sent it for lab testing. I never heard from them again. My customer bought another used strut.

Small parts can be zinc galvanized with a propane torch. They sell zinc rods at the welding store.
Heat it up and rub the zinc on.
 

TFF

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The parts are baked as part of the process to prevent the hydrogen embrittlement. At what step I don’t know. A bumper is not baked.
 

geaton196

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I took a Cherokee nose wheel strut to a chrome shop. Got a call back and the shop said the steel tube strut cracked while they were rechroming it. He said they sent it for lab testing. I never heard from them again. My customer bought another used strut.

Small parts can be zinc galvanized with a propane torch. They sell zinc rods at the welding store.
Heat it up and rub the zinc on.
Is this safe? I was admonished to never weld galvanized parts. Does the zinc rod melt without fumes?
 

wsimpso1

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All kinds of partial info on here...

All electroplating (or acid washing) of steel can diffuse hydrogen into the steel - leave the hydrogen in and you can develop hydrogen embrittlement. Reputable shops will electroplate, immediately rinse and then bake steel with very little time in between processes. Baking drives the hydrogen off. This includes copper, nickle, chrome, triple plating (copper then nickle then chrome that we are accustomed to as shiny "chrome").

I had a torque converter part that was acid washed to remove some rusty corrosion (our plant let it sit beyond the known protected time) and the springs broke into pieces as it sat on my desk over a couple days. The phenomenon is real.

If I were concerned about a hinge in an appearance area corroding and liked bright metal, I would go either electroless nickle or hard chrome. There is a whole family of corrosion proof coatings that look good. Find a guy doing them near you and ask questions about how they prevent hydrogen embrittlement, how each product holds up over time and in the weather, etc. If they are any good at all, they will tell you if baking is needed (electroless processes may not need it and they will say so), how long each coating holds up under salt spray, etc.

There are also spray (airbrush or spray gun) then bake anti-corrosion materials that can be had in MANY colors that are absolute proof against corrosion.

Billski
 

BBerson

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Is this safe? I was admonished to never weld galvanized parts. Does the zinc rod melt without fumes?
The fumes from welding galvanized steel is much worse because the zinc gets vaporized into thick white fumes. Don't breath that.
Zinc coating isn't welding. Just get the part hot enough to melt the zinc, remove the torch and then rub it on. Don't heat the zinc rod with the torch. Sort of like soldering. After zincing it can't be welded safely without grinding away the zinc.
Do this zincing outside. Only for small parts. I did a 2" sample. No actual real parts.
 

Hot Wings

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Another vote for the electroless nickle. There was a shop in my town for a while and a friend worked there. Got all kinds of things plated for a VERY reasonable cost. As noted above, just make sure that the entire process from pre-cleaning on won't promote hydrogen embrittlement.
Some of us even prefer the satin finish of the nickel over the shiny chrome.
The nickle can reduces the friction of the hinge and if it's baked after application the hardness can be increased*. My plated and baked UZI parts are just like new after more than a decade.

There are also DIY electroless nickle kits on the market - if you don't have a local shop to do the work.

*depends on the chemistry of the particular nickle system.
 

Kyle Boatright

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Electrolysis Nickel is not shinny, Show Nickel is but both tarnish as soon as they come into contact with water and will turn from pretty to pretty ugly quickly.
These are exposed, but not in a prominent position. It wouldn't bother me if they were dull. I'm looking for something which won't rust or cause a material failure down the road. Arguably, I'm over-thinking it, but it is my party, so...
 

Rik-

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These are exposed, but not in a prominent position. It wouldn't bother me if they were dull. I'm looking for something which won't rust or cause a material failure down the road. Arguably, I'm over-thinking it, but it is my party, so...
Here is an example of a polished item coated with "show nickel". It has a somewhat polished stainless look to it with a slightly "wheat" tint to it.

Don't know if this helps.
 

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wktaylor

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KB... I suspect You may be skilled-enough to 'do it yourself' by 'brush [selective] plating'...

See latest version of MIL-STD-865 [rev E?] SELECTIVE, BRUSH PLATING, ELECTRO-DESPOSITION

SIFCO is a well known vendor for brush-plating equipment, expendables, solutions and 'tech-how-to-data'... that I am most familiar with. There are also 'other' vendors that are established for hobbyists and DYI'ers... who need 'simpler equipment and lesser plating solutions'.

There are an amazing variety of plating solutions for single metal and 'multi-metal' [alloy] plating's.

See attached SIFCO PROCESS® - INSTRUCTION MANUAL 2010 This manual has very good technical, process/technique, practical, etc explanations...and safety do's don'ts etc.

NOTES.

For high strength steel [above 140 KSI-FTU] You should always use 'low hydrogen embrittlement solutions, just because'. IF steel strength is above 170-KSI-FTU [with threads or sharp entrant corners] or 200-KSI-up-to-240-KSI FTU for smooth parts, then I strongly recommend You should accomplish a hydrogen embrittlement relief bake ' to err on the side of caution.

'We' brush plate small parts all the time... cadmium, zinc-nickel, nickel, chromium and chromium over 'flash nickel' [for enhanced base-metal corrosion resistance].

Bare metal SURFACE PREPARATION is the key to success. The thin [0.0003-to-0.0008 thickness] plating's will NOT hide rough/ragged surfaces... the smoother the prettier.

ALSO... always try to smoothly radius sharp corners at least 0.020 or more, to allow plating to adhere 'around the corner'. Sharp edges will not accept plating or paint... leaving the edge to crack/peel... exposing bare metal.
 

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