I'm trying to find more information on pickling of high strength steels prior to galvanizing and the potential for hydrogen embrittlement. Our use requires components that meet the Charpy Impact test of 20J @ -20 C. We recently learned our contractor is 'flash' pickling the above items. Is there a steel strength that can be used as a guideline to switch to mechanical cleaning rather than pickling to avoid embrittlement.

Rick David Hendrix is correct that ferrous alloys with T.S > 150 KSI is susceptible for low temperature (ambient conditiion) delayed HE. The limit - to my remembrance -is still lower at 120 KSI (i.e., ferrous alloys are susceptible to low temperature delayed HE even at room temperature at 30 deg cent) even when T.S is aruond 120 KSI. I had diagnozed failures due to delayed H.E at room temperature conditions in elevator buckets and bolts when T.S was around 120 KSI in plain carbon or AISI 4140 grade materials. Bolt material used was ASTM B 7 which is near equivalent to AIS 4140 grade. AISI 4140 grade in Q&T will be more susceptible to delayed HE if T.S is even 120 KSI (24 HRc). One answer you could think of for AISI 4140 is to attempt double temper and bring down T.S around 100 KSI. Double temper of Q&T AISI 4140 will remarkably improve the impact strength and also reatly reduce the risks due to delayed H.E. Risk involved with delayed HE will also be greatly reduced if you double temper AISI 4140. Delayed H.E once exhibits or sets in AISI 4140 will make your operation difficult. Frequent failures and stoppage of plant will be the order oft he day. Trust this is of help to you. C.V.Srinivasan Nishi Engineers Pvt Ltd Chennai India June 14 E-mail:nishi@vsnl.com >Rick: > >As as rule of thumb, ferrous alloys with tensile strength >levels greater than %7E150 ksi become increasingly susceptible >to HE during pickling and electropolating. > >Hope this helps! > > >David Hendrix >The Hendrix Group Inc.