Summary for electroless nickel on b7 bolts Discussion
electroless nickel on b7 bolts is discussed as a surface-prep and pretreatment problem more than a basic incompatibility with the alloy. Denis Moles asked whether ASTM A193 B7 alloy bolts should plate normally or whether poor adhesion and flaking pointed to cleaning issues. James Watts suggested the parts may need a strike plate before electroless nickel. Todd Osmolski said hardened or high-strength steel requires different pretreatment than low-carbon steel. Guillermo Marrufo identified B7 as a high-strength fastener specification usually made from 4140 or similar heat-treated steel, and recommended a Wood’s nickel strike before EN plus a post-bake to relieve hydrogen. In a later follow-up, Rick Morgan described black coating and smut after nitric acid descaling and asked whether it was carbon or quench residue, noting that desmut steps helped only partially. The thread overall points to careful pretreatment, possible strike plating, and hydrogen relief rather than a simple alloy-plating incompatibility.
Q. Am experiencing a problem where a local plater is having difficulty depositing electroless nickel on B7 alloy bolts (ASTM A193). The result is poor adhesion, with the plating flaking off in small pieces. I suspect the root cause of the problem to be related to a poor surface preparation/cleaning operation prior to plating? Can anyone tell me if the B7 alloy poses a problem for the electroless nickel process or should this material plate-up without issue?
Denis Moles
– Foxboro, Massachusetts
2003
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A. I have no clue as to what B7 is, but another possibility is that it is a metal that requires a strike plate before the EN.
James Watts
– Navarre, Florida
2003
A. I don’t know what a B7 alloy is. Assuming it is a hardened and or high strength steel it needs to be pretreated and plated under different conditions than would be acceptable for low carbon steel.
Todd Osmolski
– Charlotte, North Carolina, USA
2003
A. B7 is a specification for high strength steel fasteners normally made up of 4140 or similar alloy heat treated steel. It should be given a Wood’s nickel strike ⇦ huh? prior to EN and a post-bake to release hydrogen. Other preparatory steps per conventional procedures.
Guillermo Marrufo
Monterrey, NL, Mexico
2003
March 5, 2014
Q. Did you ever find a solution to this problem?
I have a similar problem with plating Nickel onto ASTM A193 B7 fasteners. I believe it is due to the black coating that is on the parts following the heat treating of the 4140 steel to satisfy the B7 standard.
I remove the black material (unknown metal oxides?) with 10% HNO3 but it leaves quite a bit of smut. I assume this black smut to be elemental carbon, but 4140 is such a low-carbon alloy that I find this hard to believe as well.
4140:
Typical Chemistry
Carbon 0.42%
Silicon 0.30%
Molybdenum 0.20%
Manganese 1.00%
Chromium 1.00%
It has been suggested that the carbon smut is a result of the oil quenching process which can leave much carbon on the surface. However, I cannot verify this.
I would like to know if anyone has had a similar problem and a good solution?
My attempts were to use a HNO3 desmut and an HNO3/NH4F*HF desmut. Both worked *somewhat* but not fully (even at high concentration).
Any ideas?
Rick Morgan
– Seattle, Washington USA
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