overchrome

Re: HEX chrome on hard steel

I have a project to add a layer of chrome, about 1-2 mils thick, to a piece of OD round stock. The piece is made from hardened heat treated 1045 steel. My concern is with adhesion. From past experince I know that the harder the piece being plated the harder to get the chrome to adhere. As of now I run my tanks around 130 degrees and use a reverse etch of about 30 seconds to 2 minutes to do my plating. This is done in a seperate tank that has the same make-up as my plating tank.

How hard can stock be before you cannot get it to adhere?
Is there a different process that I should use to plate this type of steel?
Would using a different chemical to etch help?

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Labrat

Re: HEX chrome on hard steel

This is normally the process used for hard chrome plating on steel. However, if you have adhesion problems, you could try a more agressive approach - soak clean (high alkaline) - electroclean (high alkaline) - electrolytic hydrochloric acid prep (reverse current/direct current/reverse current), rinse well, reverse current chrome etch, chrome plate. Another option (if permitted for appearance) is to sandblast after the alkaline cleaning step, then repeat the entire prep sequence stated above.

Hope this helps,
Shane Moore

overchrome

Re: HEX chrome on hard steel

I don't have to  much trouble doing hard chrome on most steels. Currently I prep, scotchbrite, naptha wipe, rinse and repeat, reverse etch in chrome, and chrome. I also do a water break test. I found this process works good except for really hardened steel. I don't think the problem is in the cleaning, I believe it is the etching process. I am going to look into a hydrochloric acid prep process.

After sandblasting steel how much prep do you have to do to it before you can plate over the sandblasted area. Also what media should be used? Currently I have the ability to blast with a fine GLASS bead.

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Labrat

Re: HEX chrome on hard steel

The glass bead should work. If the glass beads seem to break down before producing a noticable etch, may need to use something more aggressive, like aluminum oxide. Make sure the part is thourougly cleaned before blasting, blast, then reverse current chrome / direct chrome plate.

Shane

overchrome

Re: HEX chrome on hard steel

Well I attempted a test piece using your advice. The only step that I changed right now from my normal process was adding the SANDBLAST. I also Increased the length of the etch time. And it is hard to believe that just those little added steps allowed the chrome to adhere. It also turned out a little brighter. I am not sure exactly why the SANDBLAST made such a difference, but it did.

Thanks for the advice. I will post back when the other piece comes out.

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thechuz

Re: HEX chrome on hard steel

If its been heat treated you probably have heat-scale on the component which can make the adhesion poor/ non existant. A HCL pickle can remove this scale most of the time but theres potential for hydrogen embrittlement which probably wouldnt be an issue for that strength material. A sulphuric etch can help alot for the higher tensile materials and if there is a significant silicon in the steel (e.g. 300M) a sulphuric/HF etch works a  treat. Grit blasting usually does the trick on most metals followed by a good strike. Dont leave a grit blasted component to long before plating though (hours) as it is a lot more likely to corrode. Grit(sand) and Vapour(wet) blasting are very effective at livening up the surface and removing oxide layers which can make the component passive.

overchrome

Re: HEX chrome on hard steel

Thanks far all the help. The piece I plated came out exactly like I hoped it would. I also found a secondary problem that I think was effecting the process. We rube all our pieces with scotchbrite after the prep before we plate, and for some reason the TECH prepping the piece used the wrong scotchbite. He used one with aluminum oxide in it. I think this might of been an issue that caused some of the pitting.

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