A193 B7 Cadmium Plated Bolts for Process Piping 1

[massad]

Can someone tell me code reference ASME or API , where it is mentioned that Carbonsteel Bolts(cadmium plated) can be used for process piping (refinery service) and either cadmium plated bolts should be used or quenched bolts ??

 

[rconner]

At least in the in the USA, (while I guess there could still be some old specification references to same) I believe there are environmental/toxicity issues associated with cadmium, and I you might find such fasteners now quite hard to get. You can find a discussion of some of these issues at the site

http://www.environmentalsupportoffice.com/Links/AMSS-Cd/Documents/Detail_Report.pdf

(see e.g. quote from this, "Cadmium is highly toxic, and a known human carcinogen.")

 

[kenvlach]

There are 2 problems with cadmium plated bolts.

Re environment & health (not counting legal restrictions in the electronics & automotive industry), ASTM B766, in the non-mandatory section, advises electroplated cadmium not be used at or above 225 ^oC (437 ^oF) nor subected to heat from soldering, brazing or welding, because of the danger from poisonous cadmium oxide vapors. Every cadmium-plated item that may be subjected to heating should be tagged & labeled.
Since one purpose of cadmium plating is solderability, either use low melting solder or take precautions against vapors (or both).

The second hazard is solid metal induced embrittlement (SMIE).
"Accordingly, cadmium-plated steel bolts, despite their excellent resistance to corrosion, are not recommended for use above 230 ^oC (450 ^oF)."
-- page 393 in ASM Handbook Volume 13A Corrosion [etc.] (2003).
Worst cases shown in the Table 'SMIE in steels,' (p. 395 ibid.) are 4340 & 4340M embrittled by Cd at 38 ^oC (100 ^oF). For 4140, the lowest temperature reported for SMIE due to Cd is 188 ^oC (370 ^oF).

Cadmium also embrittles titanium (Ti-6Al-4V & Ti-8Al-1Mo-1V, delayed fracture test) with an onset of embrittlement at 38 ^oC (100 ^oF).
Cd also embrittles Zircaloy-2 at 300 ^oC (572 ^oF).

Of course, liquid metal induced embrittlement (LMIE) is worse than SMIE for susceptible materials.

However, 304 SS has been reported as immune to embrittlement by both solid & liquid Cd.

Re ASTM A193/A193M-06a Standard Specification for Alloy-Steel and Stainless Steel Bolting Materials for High Temperature or High Pressure Service and Other Special Purpose Applications.
This spec. doesn't mention any plating (although I don't have the latest revision). IMHO, the use of Cd-plated B7 chromium-molybdenum steel (~4140) bolts at high temperature would be suicidal w.r.t. liability in the event of failure.

 

[STYMIEDPIPER]

kenvlach
Great dissertation--vert information