Cadmium plating hi tensile studs 1

If the cadmium is deposited by an electroplating process, then yes, hydrogen embrittlement becomes a concern. The conventional practice is to perform a baking operation after plating but before chromating to relieve the fasteners from hydrogen embrittlement. SAE-USCAR 5 Avoidance of Hydrogen Embrittlement of Steel has the following requirements:

320 HV < core hardness < 380 HV: bake minimum of 4 hours at 200 +/- 5 C within one hour plating and before chromate treatment.

350 HV < surface hardness < 400 HV: same as above.

core hardness > 380 HV or surface hardness > 400 HV: bake minimum of 8 hours at 200 +/- 5 C within one hour of plating and before chromate treatment.

Since you did not list a fastener standard, I do not know what &quot;hi tensile&quot; means regarding the proper embrittlement relief. If the steel has been tempered at a temperature less than 200 C in order to attain the necessary mechanical properties, then the fasteners should be baked for a minimum of 8 hours at 115 +/- 5 C.

I would not recommend using cadmium plated bolts manufactured from medium carbon alloy steel for this type of application, especially if they are not produced to a proper fastener standard (ASTM, ISO, etc.). Nickel alloy or multiphase alloys (nickel-cobalt-chromium-molybdenum) perform much better in this type of environment, and with a suitable combination of cold working and heat treatment, can attain the necessary mechanical properties. I recommend you read the following article on multiphase fastener alloys from SPS:


They also have an excellent booklet on these alloys called Superalloys Developed by SPS Technologies for Aerospace Fasteners which you can obtain by clicking on the following link:

I just came across a technical article from Avesta Polarit discussing fasteners for seawater applications:

Cadmium can be plated without hydrogen embrittlement. This is done for aircraft industry.

For info. contact Ron Saleker of Sifco Selective Plating 216-524-0099.

BarryMartin,

Zinc can too - the process is mechanical plating, rather than electroplating. If a member searched this website, and others, they would learn about cadmium vapor deposition, etc. There are numerous coatings, processes, vendors, info sources...

I mean cadmium _vacuum_ deposition in my previous message.

I think I missed the question. Concern is whther the cadmium plating protects the high tensile substrate from hydrogen embrittlement when it is subsequently part of a cathodically protected subsea pipeline.

I would have concern about high strength materials in these applications, if you cannot find a way to prevent current from being applied after instalation. You might consider a way to cover the fasteners, to minimize any current reaching the fastener.