Chrome engine mount

[RV7Guy]

Has anyone ever stripped the engine mount and had it chromed? Could be expensive but wonder if would change the characteristics of the metal.

[DeltaRomeo]

Originally Posted by RV7Guy

snip....but wonder if would change the characteristics of the metal.

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.

[rocketbob]

It can be done right without causing problems with hydrogen embrittlement if the part is baked in an oven after the part is chromed. The chrome shop I've had do work for me did this.

Link to background info: http://www.duro-chrome.com/docs/article.pdf

[Sig600]

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.

[larryj]

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.

[Zero4Zulu]

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.

[Captain Avgas]

Originally Posted by DeltaRomeo

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.

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.

[Captain Avgas]

Originally Posted by larryj

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.

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.

[Captain Avgas]

Originally Posted by Zero4Zulu

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.

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.

[sprucemoose]

Originally Posted by Captain Avgas

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.

Engine mounts are typically heat treated after welding. I'm pretty sure but not certain that Van's mounts are.