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Oil leakage through hard chrome layer





September 24, 2010

Hi everyone,

First I'm Carlos, from Brazil and I'm glad to know this huge metal finishing database.

We, at my company, are facing some problems with our hexa-chromium plated hydraulic components.

Our costumers are reporting oil, and in some cases gas, leakages during use (at normal conditions).

We've just started to analyse our whole process and I'd like to know if everyone else faced this problem?

I think, the pressurized oil takes some channel (maybe cracks linked) and it goes through ... appearing outside this system.

Carlos Rodrigues
Employee - Sao Paulo, Brazil



September 30, 2010

Dear Calos,
I can understand you have a problem, but unfortunately your question is incomplete for anyone to answer on dot.
For eg., size of component,chrome layer thickness, any kind of post grinding/finishing done after plating or not? Are yu sure the finished layer is free of any defects like peeling etc..you talk of both oil and gas? (confusing) maybe you can send a pic of the leaking part which may help anyone answer your question in more detail.

vikram dogra
Vikram Dogra
Irusha India - Chandigarh, India



October 4, 2010

Carlos,

I encountered this phenomenon a few years back where hydraulic fluid appeared to be leaking through the hard chrome plate coating. After some extensive analysis it was found that that the hydraulic fluid can be forced through the microcracking in the plating, but the pressures involved were well beyond anything you would normally see in a hydraulic system.

A strip down of the offending units found that it was not the plating that was at fault, but a seal that had not bedded correctly. This occurred on several units and a change in the profile of the seal solved the problem.

I would suggest that you look at the complete assembly as it is unlikely that the plating is at fault unless there are gross defects in the plating such as visible pores or macrocracking.

Brian Terry
Aerospace - Yeovil, Somerset, UK



September , 2010

Hi.

I am not questioning Brian's good advice, but I just happened to stumble across an old thread on finishing.com that sounded perhaps relevant: letter 7379.

Regards,

Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey



October 5, 2010

Good advice Ted,

Carlos, always worth investigating all potential solutions!

Brian Terry
Aerospace - Yeovil, Somerset, UK



October 13, 2010

Brian and Ted.

Thanks so much!

Ted, your suggestion was great. But I don't know how to obtain PS11501 and I didn't find a supplier to make some tests. Do you know anyone?

Brian, we have a team that's working on seals and they are looking for new kind of seal.

We did microcracks counting and we've found less than 500 microcracks per inch. And that's our goal, how to increase the number of microcracks. ( Nowadays we are trying to use current at minimum value)

Best Regards

Carlos Rodrigues
- Sao Paulo, Brazil


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