TheSamba.com :: View topic - Early 911 Magnesium Intake Manifold / Oil Pump / Chem. Treatment

Mon Mar 16, 2020 12:56 pm

Chem. treated a customers early magnesium Porsche 911 intake manifolds for his concours restoration. This finish will not come off with fuel nor burn off.
Duplicates factory's finish. I can perform this service for your restoration also. Cheers ; - )

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Thu Mar 26, 2020 1:28 pm

Alodine/Bonderite 5200 coating for magnesium.
Nice stuff!.

Ray

Mon Mar 30, 2020 11:18 am

Does this process cause hydrogen embrittlement? If it does, the studs should have been removed before the process was done. Just wondering. Tom

Thu Apr 02, 2020 11:12 am

Tom_Kathleen wrote: Does this process cause hydrogen embrittlement? If it does, the studs should have been removed before the process was done. Just wondering. Tom

No....chromate conversion coatings generally do not cause hydrogen embrittlement. And....HE is directly related to tensile strength of the steel. You might see some risk on very high tensile strength bolts like class 12.9...but only if you put them into use very quickly after chromate conversion coating....like less than 24 hours.

Also hydrogen embrittlement is a function of the electrolysis of electroplating and sometimes the electrolytic action of high end electro-less plating.

Hydrogen embrittlement with zinc electroplating is typically about 65% positive to occur and only about 25% positive to occur with electroless nickel for instance. This is neither of those.

Ray

Thu Apr 02, 2020 12:33 pm

Thanks for that information. I was just trying to put out some cautionary thoughts because of an experience I had with HE.

I had some brake rotors nickle plated with the 1/2" high strength (Morroso) studs installed on a buggy build. As you build a car, you tend to put it together and take it apart as you work on it. One of the times taking the wheels off, the stud galled a little bit and I kept taking if off. The stud snapped in half with very little force on it. If we had been driving the car it would have been a disaster. Replaced all 20 studs and learned a lesson. Tom

Thu Apr 02, 2020 2:35 pm

Tom_Kathleen wrote: Thanks for that information. I was just trying to put out some cautionary thoughts because of an experience I had with HE.

I had some brake rotors nickle plated with the 1/2" high strength (Morroso) studs installed on a buggy build. As you build a car, you tend to put it together and take it apart as you work on it. One of the times taking the wheels off, the stud galled a little bit and I kept taking if off. The stud snapped in half with very little force on it. If we had been driving the car it would have been a disaster. Replaced all 20 studs and learned a lesson. Tom

A couple of things:

If it was electroplating.....that was directly the cause of hydrogen embrittlement.

For electroplate.....its first a cleaning soak in caustic soda. That can cause a little bit. Many high end platers will dip in caustic, weak acid dip to neutralize for maybe 1 minute....rinse...and within minutes go into a 2-3 hour 370-400F de-stress bake. Then into a cleaning solution like tri-sodium phosphate to improve wetting.....and then into the electroplating bath.

From there....it has ro go through a quick neutralize bath....and any "carding"....which brushing or surface polishing....must be done in minutes. The parts then go into a bake just pike the other one....but upwards to 3-24 hours. That bake is what prevents hydrogen embrittlement.
The higher the tensile strength of the steel the more risk and the longer the bake.

Now....about your nickel plating. First....totally wrong plating material for bolts. There WILL be problems.

If you need nickel and are worried about hydrogen embrittlement....you use ELECTROLESS niciel plating. More expensive...much tighter control and much more even than nickel ELECTRO-PLATING......and rarely causes significant HE. A 2 hour bake would fix any potential problems.
So if they were nickel ELECTRO-PLATED.....yes.....you have hydrogen embrittlement unless they were baked.

However the REAL problem with nickel is this:....while nickel is superb because it NEVER corodes......however.....unlike zinc....it is NOT a sacrificial anode. Zinc can protect metal that it is not even on. For example you csn put a apot of zinc plating 1/2" in diameter on a steel ppate.....and it prevents rust in an area larger than its diameter. This is because its prptection is electrolytic. Where its charge potential can extend influence it prevents rust....by slowly corroding itself....creating that white dusty powder residue (zinc oxide) called white rust.

Nickel will NOT do that. While it will never rust itself.....if you scratch the surface....it has no anodic protection....so the surface underneath will begin to rust....and will rust LATERALLY in all directions, undermining the nickel plating and cusing it ro bubble and fall off in sheets....while doing severe damage to the metal underneath.

Zinc on the other hand.....if you put a scratch on it....it still protects that scratched area.
Ray