Pump industry has been relatively mature, the development of new type of pump design and coating technology has made obvious progress, yu machinery hydraulic diaphragm metering pump manufacturer today taught several ways to reduce the pump corrosion and abrasion.

Appropriate material selection

For pump manufacturers, the key is to use the most suitable substrate to reduce the corrosion problem. In some applications, the preferred use of carbon steel or cast iron material for consideration of cost factors can accurately estimate the corrosion rate. According to the acceptable annual corrosion rate, the service life of the pump can be estimated and the maintenance cost of the pump is included.

If the expected corrosion rate is not acceptable, the pump material must be upgraded to stainless steel, which will lead to increased costs. If such a cost increase is not acceptable, the alternative is to use advanced coatings based on the characteristics of each application.

If an application chooses stainless steel as the base material, the expected service life of the pump can be extended a lot, in some cases even infinite. However, only the appropriate stainless steel grade for the specific application, the pump is carefully manufactured and the pump can be used according to the required fluid specification to ensure that the pump life is long enough. Once particles are introduced into the fluid, you need to be especially careful.

In this case, even the stainless steel is liable to corrosion, because as the passivation layer is destroyed, the substrate becomes activated and begins to corrode. The passivation layer can usually be reestablished, but if the chloride content is too high or the pH is too low, the material may remain active and the corrosion continues. Another common cause of corrosion of stainless steel pumps is the stagnation caused by process interruption or intermittent operation.

Another threat to stainless steel is chlorine, which is mainly used to control the growth of the creatures in the pump or in the pipeline. About 2 PPM of low concentration of chlorine almost won't cause what effect to stainless steel, but it's important to understand how and where chlorine were introduced into the water, in order to avoid damage due to a high concentration and protective layer.

Compared with cheaper carbon steel materials, accidental corrosion easily offsets good expectations of the durability of stainless steel.

Protective coating

To clear the following two problems is very important, first of all, the application of protective coating really can improve the performance and service life of the pump, second, the coating is actually less than the cost of material the cost of the upgrade. In most cases, the pump manufacturer tries to meet the requirements of the production process by using materials that are most suitable for the application, while using the coating as a backup solution.

Polymer coatings such as weld epoxy can be applied to a pump assembly using a fluidized bed or electrostatic coating. As long as the coating is not damaged, they can have a good anti-corrosive effect. As a kind of polymer coating, it is limited for low flow conditions, and is typically used for clean water applications, applications in such environment, it can be controlled by a smooth surface to improve the hydraulic performance of pump.

However, the coating applied to the pipe may not be applicable to pump applications, because in the pump application, the flow rate is much higher and the narrow channel concentrates the flow and the moving parts are difficult to protect. Therefore, some methods commonly used in piping (such as electrocorrosion) are not suitable for pumps.

In these cases, the coating is applied to specific areas that are expected to increase, or where a collision injury is expected (such as a 90-degree curve). Hard coatings are usually applied using spray methods such as air plasma spraying (APS) or high - speed oxygen fuel (HVOF). Which spray method will be selected depends on the coating thickness and coating composition.

The cemented carbide coating is very durable by using high speed oxygen flame method. Optimum use of tungsten carbide with cobalt, nickel or cobalt - chromium matrix. Due to the improvement of powder and thermal spraying process, the materials not only have good wear resistance and toughness, but also have good corrosion resistance. Thermal spraying can be applied to most base materials, but it is a "line-of-sight" process, which makes it difficult to apply complex shape components such as impeller.

For those who easily coating by thermal spraying methods of complex components, can use the CVD process, it can form a hard coating, but this process needs to be done in more than 850 ℃ temperature. Such high temperatures limit the selection of the substrate because of structural changes and partial deformation during the cooling phase.