[larry53]

Has anyone used 416 stainless steel. A company in Florida makes large water pumps, they use 416 for the shafts. I know 416 is a free machining stainless but will it rust?

[HuFlungDung]

I've heard that it is not as corrosion resistant as 304 or 316, but in pump service, immaculate appearance may not be uppermost in desirable features. The more corrosion resistant grades like 304 or 316 are a bit finicky when it comes time to push bearings or wear sleeves on and off the shafts.Often, they will gall extremely badly, ruining the shaft on the first overhaul.

416 has improved corrosion resistance if it is heat treated, too. It does not get super hard, maybe 35Rc or so, but it does machine nice in the hardened condition.

[larry53]

Thanks for the quick reply.

[wandrist]

Just to add you can surface harden 416 to 60 Rc by using nitriding.

[DonutSlayer]

Yes 416 cuts real well, and it WILL rust slightly but no where near as bad as plain steel, the most I have seen is a light surface rust.

[brookee]

Yes, 416 stainless steel is a free-machining martensitic stainless steel that offers good corrosion resistance, but it is not as resistant to rust as other stainless steels like 304 or 316. While it does contain chromium, which helps resist corrosion, it also has a higher sulfur content to improve machinability, which can reduce its overall resistance to corrosion, particularly in harsh environments. If the shafts are exposed to water or other corrosive conditions over time, especially if the protective oxide layer is damaged, there is a possibility of rust or pitting. To mitigate this, proper surface finishing, protective coatings, or using a more corrosion-resistant material like 316 stainless steel could be considered, depending on the specific operating conditions.

[cnchome-beyond]

316 stainless steel will not rust. You'd better choose the right tool when processing 316 stainless steel, which will get twice the result with half the effort. Whether it is turning or milling, the choice of tool is particularly important.

[cnchome-beyond]

416 stainless steel is a martensitic stainless steel known for its **good machinability**. It is often used in applications that require high strength and a certain degree of corrosion resistance, such as shafts, valve parts, and fasteners. In response to your question, let's analyze it in detail:

Characteristics of 416 stainless steel
1. Easy to process
The high sulfur content of 416 gives it excellent cutting performance, so it is very efficient during processing.

2. Corrosion resistance
- The corrosion resistance of 416 is lower than that of austenitic stainless steels (such as 304 and 316), but it performs well in **mildly corrosive environments**.

- If used in industrial equipment, such as water pump shafts, it usually meets the requirements when in contact with non-corrosive or weakly corrosive liquids.

3. Rusting conditions
- Long-term contact with water or humid environments** may cause surface rust, especially in environments containing chloride ions (such as seawater or chlorinated water). - After heat treatment, the corrosion resistance of 416 will be slightly improved, but it is still not comparable to highly corrosion-resistant steel grades such as 316.

Suitability for water pump shafts
- If the pump is working in an environment with highly corrosive liquids (such as salt or acid components), 416 is not the best choice and a more corrosion-resistant material such as 316 stainless steel or duplex stainless steel may be required.
- If the pump only handles fresh water or slightly corrosive liquids, 416 is an economical and efficient choice.

Recommendations for avoiding rust
1. Surface treatment
Passivation treatment** or application of anti-corrosion coating to 416 can significantly improve its rust resistance.

2. Maintenance
- Clean the surface regularly to prevent the accumulation of corrosive substances.
- Avoid long-term immersion in liquids containing chloride ions.

3. Environmental selection
If it is a hot and humid area such as Florida, with high humidity and possible exposure to salty air, special attention should be paid to material protection.

In summary, **416 stainless steel may rust**, but its processing performance and appropriate corrosion resistance make it an ideal choice for many applications. For the use of water pump shafts, the corrosiveness of the working environment and the service life requirements of the shaft need to be considered comprehensively.