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Bronze oxidation

I am R&D engineer.
I am working at diamond tools manufacturing. Some of the products we are making are from bronze.
in order to avoid oxidation we are heating the bronze to 850C in nitrogen and cooling it down to the room temperature.
in order to save time of the cooling I would like to open the oven earlier than the room temperature but still avoid the oxidation.
so my question is: "What temperature does bronze begin oxidation? Is the oxidation a continuous process as temperature increases? OR Is there a specific temperature at which all of the bronze in a sample will oxidize, then no more oxidation will occur as temperature increases?"
I am using different bronze Cu/Sn for 90/10 to 70/30, what is the differences at the oxidation temperature?

ALON GOLAN
diamond tools - Haifa, Israel
2007

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2007

Hi, there,

Oxidation is a step-change process above a critical temperature of which it will occur. This will result in a process in which either a protective (aluminum, chromium) or non-protective scale is formed. In the case of protective oxide scale formation, further oxidation is slowed down greatly and this is the case in your nitriding of the bronze (nitriding is a oxidation in a general sense).

Since O2 is more oxidising than N2, the nitrided surface of your bronze at 850C could be oxidised by further by O2 at elevated temperature during cooling, as you correctly suspected.

To find out such a safety temperature of cooling, a simple thermo analysis monitoring the tiny weight changes (from oxidation) during heating (or cooling) could yield the answer.

Hong Wei Wang
- Leatherhead, Surrey, UK