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PREN for hardchrome plating - pitting resistance equivalent number

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noirengineering

Mechanical
Aug 29, 2014
3
G`day !

Wondering is it a practise to evaluatee corrosion resistance of hardcrome plating in terms of PREN ? on any base material or would it be different on a SS304 or SS base material?

 
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PREN is meaningless with regards to hard chromium plating. It pertains to stainless steels (corrosion resistant steels).
 
PREN is a function of % Cr, Mo, W, and N and applies to stainless steels, and is sometimes used for Ni-base alloys.
 
When you talk corrosion and Cr platting the real issue is porosity.
The Cr is highly corrosion resistant, the holes and cracks, not so much.

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Plymouth Tube
 
As EdStainless points out, conventional hard chrome plating can have porosity problems. So its corrosion protection capability is not great. On the other hand, thin dense chrome plating does not have this porosity problem, so it provides very good corrosion protection. In fact, the corrosion protection capability of thin dense chrome is good enough that bearing manufacturers often use thin dense chrome plated alloy steel races in place of stainless steel races for most applications requiring corrosion resistance.
 
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