51316-7690-Atomic Hydrogen from Electroplating of High Strength Steels – How Much is Trapped in the Coating?

Available for download

Product Number: 51316-7690-SG

ISBN: 7690 2016 CP

Author: Tim Gommlich

Publication Date: 2016

Member Price: $0.00

Non Member Price: $20.00

Price: $20.00

Qty:

Titel: Atomic Hydrogen from Electroplating of High Strength Steels- How Much is Trapped in the Coating?Electrodeposition of zinc cadmium nickel or zinc-nickel on steel is accompanied by hydrogen evolution. This causes a general risk for hydrogen embrittlement specifically for high strength steels. Many efforts are made to minimize this risk by using appropriate plating conditions and processes. However to be successful it is necessary to know how much of the electrochemically produced atomic hydrogen is going into the air after recombination to molecular hydrogen into the base metal and into to plated metal. In a systematic study a hydrogen balance was made covering the whole plating period of a ZnNi plating process. Depending on the process parameters the following data were measured or calculated: the total amount of electrochemically produced hydrogen the total amount of hydrogen permeating through a steel membrane during the plating process and the percentage of permeated hydrogen related to the total amount of electrochemically produced hydrogen. Furthermore the amount of hydrogen trapped during the plating process in the steel and separately in Zn Cd Ni and ZnNi coatings was estimated by quantitative measurement of the amount of hydrogen effusing from the steel and from the coating during thermal treatment (24 h/190°C). The risk for hydrogen embrittlement of high strength steel at the different steps of the coating process was determined with constant load tests on electroplated notched tensile specimens. It was shown that metal coatings may serve as a remarkable hydrogen reservoir. Thus zinc coatings can trap significantly more hydrogen than the base metal. This trapped hydrogen can be released during thermal treatment not only out of the coating but also into the base metal causing delayed fracture of the steel.