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Rust on electroless nickel parts

2004

Hello,

The problem we are having is rust. These components are made from A2 tool steel, (non-heat treated), and are electroless nickel. Could this problem be a bad nickel job, and is there a better process on steel for our needs? These part are used in a clean room for component assembly.

Regards,

Dennis Leto
Semiconductor Industry - Tucson, Arizona, USA

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First of two simultaneous responses

The first probbility is the coating is too thin. 0.0005 should be an absolute minimum, and since you are experiencing rust, probably closer to 0.001".

since this is a clean room, it should not be rusting at all. There is a reasonable probability that someone that is using or has handled the parts has very acid sweat. One place that I worked had a person in the tool room with sweat so bad that bare A1 parts would have rusty finger prints over the lunch hour.

James Watts
- Navarre, Florida
2004

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Second of two simultaneous responses

What does your plater have to say about this? EN on A2 should not be a problem. What is the thickness? You may need about .0005" minimum to avoid rust.

Jeffrey Holmes, CEF
Spartanburg, South Carolina
2004

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Poor corrosion resistance of EN is simply an indication that the coating is porous. Poor pretreat is one likely cause, high turnover bath might be another, but my guess is that the wrong EN might be the cause. High phosphorus EN costs more but the amorphous coating which is far less likely to contain pits or pores more than makes the difference worth it! If you want high quality, spec out high phos - see spec ASTM B733 which grades the types of electroless nickel according to phosphorus content. I believe Type V is the one that refers to high phos.

Milt Stevenson, Jr.
Syracuse, New York
2004

What type of EN are you using? The type and percentage of additives will have an effect on the porosity of the coating. The age of the EN solution will also have an effect om the porosity. If I wanted a corrosion resistant coating I would not consider using anything less than 0.001", if the coating is plated out of a low phosphorus process I would consider going even thicker than that.

Brian Terry
helicopters - Yeovil, Somerset, UK
2004