What is hidrogenation when zinc electroplating? 1

[pardal]

Hi all Material people:

I'm dealing with zinc electroplating bichromatizing it to yellow or black .
I do not know nothing about this matter , but I need to do this process at this materials.
on AISI 1010 cold die formed, Aisi 1070 laser cuted,
Aisi 1070 heat treated to RA 68-75 .
Both steel could be yellow or black finish.
The AISI 1070 are under elastic deformation as in flat spring.
When I went to the electroplating shop , they warning me about the "hydrogenation" that the steel will suffer and the need to do a "dehydrogenation process" to this materials.
With this in sigth , I do a search for "hydrogenation steel"
and it seem that this problem doest noy have to do with zinc electroplating.
Maybe I'm wrong, sure.
Could any one explain about this facts?.
Best regards.
Pardal



















Pardal

 

[nashjp]

Pardal,

The hydrogenation I think the are referring to is the fact that as part of the plating process the parts are dipped in an acid bath. This bath/chemical reaction provides a source for hydrogen that can enter the metal matrices. Try looking under the subject of "hydrogen embrittlement" or "stress corrosion cracking".

Hydrogen embrittlement effects hard parts HRC30+. Common industry practice is to bake such parts at an elevated temperature (375F?) for several hours (HRC30 - HRC39 4hrs),(HRC39 - HRC45 8hrs) (>HRC45 12 hrs). It is important to start baking the parts within 1hr after plating.

I do not know what your parts are, some parts do not require this procedure because they do not see tensile loading.

Well this is a start - good luck. (My expertise is not in this field so be sure to check my temperature, hardness, and durations with someone who actually gets paid to do this)

 

[TVP]

Pardal,

nashjp gave you most of the information correctly. Electroplating in a water-based solution will always generate free hydrogen, which can be absorbed by the steel during plating. Baking after the plating treatment allows for the liberation of hydrogen from the plated layer, as well as redistribution of the hydrogen that has been absorbed into the steel.

As for baking times and durations, SAE/USCAR-5, Avoidance of Hydrogen Embrittlement of Steel requires the following:

surface hardness > 350 HV (Vickers hardness) or core hardness > 320 HV should be baked at 200 +/- 5 C for 4 hours prior to chromate conversion coating. Baking treatment should be performed within 1 hour of plating.

surface hardness > 400 HV or core hardness > 380 HV, should be baked at the same temp for 8 hours prior to chromate conversion coating, and withing 1 hour of plating.

If hardened parts have been tempered at less than 200 C, then the baking cycle should be 115 C for 8 hours, again within 1 hour of plating.

 

i have found a good, used, out of print electroplating books and related topics at:

http://www.geocities.com/alinoph/electrobooks.html

thank you

 

[Bugman]

Some good information at

http://www.azom.com/details.asp?ArticleID=1407

 

[pardal]

Hi Al2002 and Bugman. thanks for it Pardal