This hydrogen embrittlement thing has had me worried, so I contacted two local platers who service the oil patch here in Calgary. They do all sorts of pump/compressor parts for the industry as well as doing stuff on the side such as automotive, no problems getting cad though, zinc is actually harder to get on this side of the border.

Both platers said exactly the same thing...namely that the hydrogen embrittlement question only really applied to extremely high criticality, highly stressed parts or fasteners and they had never seen any part fail or be at risk to fail in automotive use due to hydrogen embrittlement. They knew what it was, they knew how to deal with it and had the equipment to bake, but they basically said they would not do it as they would just be "stealing my money" when it came to automotive parts. Only thing they said they would not plate was springs (e.g. in our case torsion bars) that were hardened and highly stressed.

So, I remain confused. I replated all of my '75's fasteners, it has been 14 years including a few track days, there has been zero problems. I have plated the suspension bolts as well as more lowly fasteners and have yet to see any issue at all....so, what is a guy to do?

Dennis

Slightly off-topic, but...

Instead of Cd (or Zn) plating, what about replacing the fasteners with 316 ss?

I know this would only be possible for the metric hardware and not the speciality parts, but it would seem to be a reasonable solution, and one that I'm using for my work in progress.

Subscribing for info purposes... interested in answers to using SS vs cad plating.

Thanks.

My understanding is that SS hardware is not very strong. Good for holding on fenders and bumpers, but probably not much more. Just what I've heard from folks who know.

OK, so I did some research...

According to my sources - standard metals handbook info - standard-grade 316 has a tensile strength of 515 MPa, min., while SAE J249 grade 5 is about 40% higher. Grade 8 is quite a bit higher than that at about double the tensile strength of 316, but how many bolts in a car are actually grade 8?

So - I think your sources are correct.

For applications where fastener loading is not critical, 304 (18-8) or 316 fasteners would be ok, but I personally will not use them on suspension, steering, or other critical high-load areas. FYI, I am in the process or using them to hold my rear bumper on and secure my Fabspeed/Dansk exhaust system.

+1. Only use SS fasteners when the part that falls off won't kill you or damage the vehicle. Why chance using a weaker material in a critical, high-stressed area of a car?

Sherwood

I still wonder, however, how many of the threaded fasteners on our Porsches are actually grade 5 or grade 8, that is metric 8.8 or 10.9?

One could, I suppose, go for one of the stronger corrosion-resistant alloys, but metric hardware made of Ni-based alloys - like MS14181 Inconel 718 or better yet Carpenter MP35N don't seem to be all that readily available, unless one has a connection to an aerospace supplier. Notably, the mechanical properties of these materials are even better than grade 8.

pretty much every bolt i've plated at home has been marked 8.8
front and rear sway bars, caliper mounts, control arms, even brake dust shield bolts are 8.8.
haven't seen a 10.
plan on popping them in an oven at 375 for three hours according to the caswell people
although they too maintain its probably not necessary for automotive plating.
more important in aircraft, no surprise there.
i will say i plated those spring clamps on the trunk heater boxes to pretty them up.
half of them snapped like dry twigs when i tried to install them!
they are made of spring steel however and quite thin gauge

seat bolts 10.9??

engine studs (natch)

case thru bolts?

flywheel bolts

CV bolts of course

caliper thru bolts (star head ones)

what else might be high strength?

Shaun, Did you ever have your items plated? Just curious how that place in Texas worked out?

As I said earlier in this thread, it's a disease. I've added another 2 cars worth of hardware to the piles and have another half a car to sort and add. I'm hoping to ship everything out at the end of January, though I found one locally, just need to ask if they bake.

Thanks, I was just curious. Im also getting ready to send a bunch of stuff out.

Where are you sending it?

Im using a local plating company that we use here at work.

Missing parts, KC911 is right... especially with small parts. You can help your vendor by making a detailed inventory and accompany the "lot" with a picture. None of this will prevent the loss of a part (s), but it will make the vendor aware of who he's dealing and with the importance of the parts he's working with.

I've found that the bead blasting preparation has a lot to do with the final uniformity of the color of the cad or zinc plating. If you use a too aggressive media then the final color can be modeled. Ask me how I know...

I would also put in writing any directions as it relates to "baking" structural parts as it relates to the prevention of Hydrogen Embrittlement.

Any suggestions on a good blasting media to use?

I have a mixture of several different medias that are OK for general clean up, but turn out to be too aggressive for the plating prep. Which I only found out after the plating was done. Probably soda blasting would be best. I've never tried it... I think it's messy (dusty) to use?

Next time I spend the money for plating I'm going to do some investigation on prep. It could be my platter, but he says that it's my bead blasting that is giving the plating the modeled finish... In the long run it might be better just to find a plating service that will take your dirty parts and process them from beginning to end. Then you know it's done right.

I think a more interesting discussion is what is the better finish, Type II Cad (yellow) or Zinc plating? Differences in cost, durability, color, originality, etc?

The hydrogen embrilltement should be a concern with regards to bolts of grade 10.9 & 12.9 DIN. Some bolt manufacturers will not yellow zinc these due to this issue. Porsche has few 10.9 & 12.9 class bolts on the chassis. The spring plate to swing arm bolts (4 M12X35) where upgraded in '83 from 10.9 to 12.9, together with a higher torque value.
When you order these bolts from Porsche they come with a yellowish/green coating, definitely not zinc or cad. The same goes for the conical tranny bolts that secure the cross member to the chassis. The M14 swing arm pivot bolt is grade 8. The caliper mounting bolts are M12's, also 8.8 DIN.
I did this exercise 3 yrs ago and had the batch baked after plating. I got a spec sheet regarding coating composition, thickness with bake time and temp.
I think with 8.8, you should be ok; 10.9 and up don't chance it. Google Metric Blue, this is a US fastener company that provides 12.9 bolts with a proprietary coating which avoids the hydro/embrilltement issue. The only bad thing is the bolts are blue!!
Now a days it's very hard to find Verbus, Inbus, Kamax, Lobo bolts; the majority is coming out of China and Taiwan. You can still find Fontana (3F & 4F (10.9), but you have to look.
I found some of the German stuff from Metric Screw & Tool Co. in Wakefield Ma.
800-METRIC-1, ask for Dave, if he's still there he can help. He also led me to the plater they used when a customer wanted a certain finsh. I can't find the name of the plater used; they where in MA.
Metric & Multistandard Co. also had some German: http://www.metricmcc.com
I found these guys for the West Coast crowd: http://burbankplating.com/
Lastly Steve from Ultimate Garage in NJ used to carry German fasteners, when I went there he had a huge inventory of OEM BMW & Porsche hardware.
http://www.ultimategarage.com/

Regards,
j.p.