Why Stainless steel gear pump rust?

What is stainless steel?
Has the ability of resistance to oxidation atmosphere, at the same time, also has in the medium containing acid, alkali, salt corrosion resistant ability of steel!

Then, Why stainless steel gear pump rust?
Added on the surface of the stainless steel gear pump luo and nickel elements, such as to form a layer of a very thin and fine and stable solid rich chromium oxide film (protective film), prevent oxygen to infiltration, continue to oxidation, and ability to resist corrosion.

Why stainless steel gear pump will rust?

When the density of oxide layer are destroyed, stainless steel pump will rust.

What conditions would destroy the protective film?

1) bleaching powder (2) mechanical wear 3. Water

Stainless steel gear pump type

Stainless steel gear pump points many types, different properties, different using environment.

For example: 304 stainless steel pump, in dry clean atmosphere, have absolute good corrosion resistance, but it will be moved to the coastal areas, in contains a great deal of sea salt fog, will soon be rusty;And 316 steel tube is good.

According to the composition can be divided into the Cr system (SUS400), the Cr – Ni (SUS300), the Cr – Mn – Ni (SUS200) and precipitation hardening (SUS600).

The 200 series – chrome – nickel – manganese austenitic stainless steel.

The 300 series – chrome – nickel austenitic stainless steel.

301, good ductility, used for forming products.Also can rapid hardening by mechanical processing.Good weldability.Abrasion resistance and fatigue strength is better than that of 304 stainless steel.

With 304, 302 – corrosion resistance due to the carbon intensity of relatively high and better.

303 – by adding a small amount of sulfur and phosphorus from 304 are more likely to machining.

18/8-304 stainless steel.GB brand of 0 cr18ni9.

309 – compared with 304 has better temperature resistance.

After 316-304, the second to get the most widely used types of steel, mainly used in the food industry and surgical equipment, add molybdenum elements make it get a kind of corrosion resistant special structure.As compared with 304, it has a better ability to resist chloride corrosion and therefore as “Marine steel” to use.SS316 is usually used for nuclear fuel recycling equipment.18/10 grade stainless steel usually also fits the application level.

321 – except for adding the titanium reduces the weld material corrosion risk besides other performance similar to 304.

Series 400 – ferritic and martensitic stainless steel.

408, good heat resistance, weak corrosion resistance, 11% of Cr, Ni 8%.

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