RV7Guy

RV7Guy

Well Known Member
Has anyone ever stripped the engine mount and had it chromed? Could be expensive but wonder if would change the characteristics of the metal.
 
RV7Guy said:
snip....but wonder if would change the characteristics of the metal.
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YES!

Van's recommends not chroming the external steps in the -A models for the same reason. Several of the chromed ones have failed. Results in Hydrogen Embrittlement .

(from a hotrodding forum) "This is the same reason that chrome suspension parts will not pass tech inspection for NHRA held events."​
Baking afterwards is done but still results in a somewhat weekened metal (but how much I can't tell you).

My .02 Darwin.
 
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Like Doug mentioned, one of the RV-6A's we were flying a few years ago had the steps chromed and the pilots side literally snapped off.

As cool as it would look, not worth the risk IMO. I was thinking about doing the same to the canopy bow/frame in my 7, until I thought about how annoying the reflections would be.
 
electroless nickel plating

An option to chrome is nickel, and electroless nickel does not induce hydrogen embrittlement. You can notice that most if not all race car ferrous pieces are treated this way. Beware that nickel can be applied 2 ways; with an electrolytic process (does induce hydrogen embrittlement) and electroless (which does not induce hydrogen embrittlement. I have all of my ferrous airframe pieces electroless nickel plated, and just because I'm old school and it doesn't hurt anything, have the pieces baked afterwards. To meet spec the bake needs to be done within 30 minutes of plating, at 400 deg F for about 4 hours. There is another spec for heat treating the nickel after plating which uses a higher heat and turns the color to straw color; functionally fine but aesthetically likely not.
 
Nickel plating looks nice but will not hold up to wear and tear. When dinged with hard objects like wrenches it will flake off leaving bare metal exposed.
 
DeltaRomeo said:
YES!

Van's recommends not chroming the external steps in the -A models for the same reason. Several of the chromed ones have failed. Results in Hydrogen Embrittlement .

(from a hotrodding forum) "This is the same reason that chrome suspension parts will not pass tech inspection for NHRA held events."​
Baking afterwards is done but still results in a somewhat weekened metal (but how much I can't tell you).

My .02 Darwin.
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Doug, this is a very technical area. 4130 steel is a low carbon, low alloy steel generally supplied by steel distributors in the normalised condition and in that condition it has a low susceptibility to hydrogen embrittlement caused by electroplating.

But many components fabricated from 4130 (such as suspension parts) are heat treated after fabrication to increase the ultimate strength. However doubling the strength of a steel invariably means quadrupling its susceptibility to hydrogen embrittlement.

My best guess is that Van's steps would be normalised 4130 (not heat treated) and therefore hydrogen embrittlement resulting from plating should not be of concern.

It is probably true that several Vans chromed steps have failed....but in the same time frame probably hundreds of Vans painted steps have failed. See photo. It's probably more to do with fat pax jumping on the step.

Personally I wouldn't have any reservations about electroplating the steps on an RV if that was the desired aesthetic.

On the other hand I would not electroplate a 4130 engine mount. 4130 steel is relatively susceptible to corrosion and getting 100% electroplated nickel coverage over the crucial welded areas could be problematic. It's a more crucial structural element so I'd be correspondingly more cautious.

 
larryj said:
An option to chrome is nickel, and electroless nickel does not induce hydrogen embrittlement. You can notice that most if not all race car ferrous pieces are treated this way. Beware that nickel can be applied 2 ways; with an electrolytic process (does induce hydrogen embrittlement) and electroless (which does not induce hydrogen embrittlement. I have all of my ferrous airframe pieces electroless nickel plated, and just because I'm old school and it doesn't hurt anything, have the pieces baked afterwards. To meet spec the bake needs to be done within 30 minutes of plating, at 400 deg F for about 4 hours. There is another spec for heat treating the nickel after plating which uses a higher heat and turns the color to straw color; functionally fine but aesthetically likely not.
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Good call Larry. I electroless nickel plated several components on my RV7A. Here's a few more characteristics that might be of interest to potential users:

1. Only available in a satin finish (but it's a nice satin finish).
2. Will throw inside cavities (electroplating will not).
3. VERY expensive.
 
Zero4Zulu said:
Nickel plating looks nice but will not hold up to wear and tear. When dinged with hard objects like wrenches it will flake off leaving bare metal exposed.
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If nickel plating comes off in the manner you have described it is simply an indication of poor electroplating technique. Properly applied it should be fully bonded to the steel substrate.

For generations cars had nickel plated bumper bars and look at the parking treatment those continuously got without chunks "flaking" off.
 
Captain Avgas said:
But many components fabricated from 4130 (such as suspension parts) are heat treated after fabrication to increase the ultimate strength. However doubling the strength of a steel invariably means quadrupling its susceptibility to hydrogen embrittlement.
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Engine mounts are typically heat treated after welding. I'm pretty sure but not certain that Van's mounts are.
 
Micro-cracks in hard chrome leading to metal fatigue

Often, oleo piston struts from landing gears are chrome plated for abrasion reason. The hard chrome layer is rather brittle and will show micro-cracks. This is good for wear and friction behavior (lubricant film) but not for metal fatigue! The micro-cracks act as stress raisers for the base material. Therefore, in avaitaion industry the landing gear parts are shot-peened before chrome plating. This introduces compressive stresses that will prevent or at least slow the metal fatigue. And then, there might be the hydrogen, as already mentioned... It also accelerates metal fatigue if present.

I would not chrome plate structural important parts without deeper knowledge of the loading and the processes. Just my two cents.
 
heat treating

I would be very surprised if any GA engine mount is heat treated after welding. Pitts mounts are not, why would an RV mount be.
I had most of the small parts on several Pitts's Cadmium plated by a shop that did work to MIL specs. The parts were baked after plating. I do not agree with chrome plating any 4130 steel structural part. Lyc rocker covers are mild steel and chroming them does not seem to cause any problems. There are vendors selling new chrome Lyc rocker covers. Lyc uses chrome rockers on their display engines.
 
Chrome ish

If you are just after looks there are new paint proceses that look exactly like chrome and powder coats that look chrome-ish or brushed nickel. The local Harley custom painter showed me the chrome paint and its impossable to tell from real chrome, except it does chip like any paint. Russ
 
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