10 Aug Electroless Nickel Plating Temperature Limits
Electroless Nickel Plating Temperature Limits
The deposit coming off an electroless nickel plating line can be a very different animal at 200°C compared to 400°C. Therefore, it is very important to know the temperature limits of the coating before specifying it.
Plating Bath Temperature
This process is typically run at a bath temperature of approximately 85°C to 95°C in order to maintain a stable reaction and to deposit an even coat. The bath temperature is an important factor to consider as a decrease in temperature will decrease the rate of deposition. Conversely, an increase in the bath temperature can cause the bath to decompose.
Service Temperature by Phosphorus Content
The low-phosphorus coatings (1%–4% P) are intended for service at continuous high temperatures up to about 350°C. Coatings with a medium level of phosphorus (5%–9% P) are intended for intermittent use at moderate temperatures, up to about 250°C. The highest level of phosphorus (10%–13% P) gives the best corrosion resistance but this has to be offset against the inability to use at high temperatures in service (surface coating performance data measures the stability of the crystalline form of the coating, below 180°C for high-phosphorus coatings).
Hydrogen Embrittlement and Baking
Steel above 40 HRC is prone to hydrogen embrittlement after plating. This can be relieved by a baking treatment at temperatures between 190°C and 210°C for 3 to 4 hours.
Hardness Gains From Heat
A coating deposited by electroless nickel plating has a hardness of around 500 HV. A subsequent heat treatment, at temperatures of around 300°C to 400°C, can increase this hardness to 900 – 1000 HV. This high wear resistance is, however, often obtained at the expense of corrosion protection.
Oxidation Above 450°C
As a general rule a nickel plate coating that is to be used at temperatures above 450°C will undergo oxidation and likely detachment from the substrate. Under these situations other coatings would be advisable.
Match your phosphorus content and any subsequent heat treatment to your actual service conditions, and you will find that the resulting electroless nickel coating performs well within its defined limits.