In fluid transport systems,the pump serves as the core power device,and its operational stability is closely tied to the continuity of the entire process workflow.However,corrosion has always been a key factor restricting the service life of the pump body.Especially in industries such as chemical engineering,petroleum,and water treatment,where the media composition is complex and the operating conditions are harsh,equipment failures caused by corrosion are commonplace.

-Bonve Pump Industry Cam-Type Twin Rotor Pump-

I.The Electrochemical Nature of Corrosion

As defined by the ISO 8044 standard,corrosion is an interfacial chemical reaction that occurs between a metallic material and its surrounding environment.The vast majority of corrosion processes are electrochemical corrosion,which can only take place in an electrolyte medium possessing ionic conductivity.The entire process is essentially a set of oxidation-reduction reactions,comprising two parallel half-reactions:on the anodic side,an oxidation process of metal dissolution occurs,while on the cathodic side,a reduction process in which ions in the electrolyte gain electrons takes place correspondingly.Once corrosion occurs,both the mechanical properties and geometric dimensions of the material will undergo measurable degradation,and in severe cases,this can directly lead to the failure of components or even the entire system.

II.Corrosion Forms Without Mechanical Loading

Under the action of the medium alone,the pump body may exhibit various forms of corrosion.Uniform surface corrosion is the most intuitive,in which the material thins at a relatively consistent rate across the entire exposed surface,and its harm is relatively controllable.Shallow pit corrosion manifests as localized recessed spots on the surface,triggered by uneven local distribution of temperature,concentration,or flow velocity.Pitting corrosion is more concealed;the concentration of localized electrochemical reactions causes the material to erode inward,forming pinhole-shaped corrosion pits.Chloride-ion-containing media are highly prone to inducing pitting corrosion in stainless steel and aluminum alloys,and once a corrosion cell forms,it accelerates the expansion.

Crevice corrosion frequently occurs at fitting gaps,where the enrichment of chloride ions or the depletion of oxygen inside the crevice damages the passivation protective layer.Galvanic corrosion arises in scenarios where metals of different corrosion potentials are in contact;the more active metal with the more negative potential acts as the anode and dissolves at an accelerated rate,with the rate depending on the potential difference and the anode-to-cathode area ratio.

Selective corrosion targets only specific phases or components of an alloy,including graphitic corrosion of cast iron,intergranular corrosion of stainless steel,and dezincification of copper alloys.Static corrosion occurs during the shutdown phase of the equipment;microbiologically influenced corrosion is induced by the metabolic activities of microorganisms such as sulfate-reducing bacteria,and positive-displacement pumps such as rotor pumps must likewise pay attention to this type of risk when handling media containing bacteria.

-A Pump Body with Material Corrosion-

III.Corrosion Types Coupled with Mechanical Loading

When corrosion and mechanical action coexist,the damage is significantly accelerated.Erosion corrosion is the synergistic effect of fluid scouring and chemical corrosion,in which high-speed fluid continuously strips away the passivation film,and it occurs at high frequency on flow-passing components such as impellers and pump casings.Cavitation corrosion accompanies the phenomenon of cavitation,where the impact force from the collapse of bubbles repeatedly destroys the protective film,and corrosion and cavitation alternate to form a vicious cycle.

Fretting corrosion occurs on fitting surfaces where slight relative displacement exists,with wear continuously removing the passivation layer.Stress corrosion cracking is a brittle crack produced by the combined action of tensile stress and a specific medium;there are no obvious corrosion products before fracture,making it highly sudden and extremely dangerous.Corrosion fatigue,in turn,is the result of cyclic alternating stress superimposed on a corrosive environment.

IV.The Core Approaches to Corrosion Prevention and Control

The corrosion failure of a pump is the result of the multi-factor coupling of medium characteristics,material properties,operating conditions,and mechanical loads.Compared with uniform corrosion,localized corrosion forms such as pitting,crevice corrosion,erosion,cavitation,and stress corrosion cracking are highly concealed,develop rapidly,and cause concentrated damage,making them the primary causes of flow-passing component failure,sharp performance decline,and even sudden accidents.

Effective corrosion prevention and control requires systematic advancement across multiple stages.During the material selection stage,priority should be given to matching corrosion-resistant alloys or easily passivated metals to ensure compatibility with the transported medium;structural design should avoid crevices,sharp corners,and stress concentration zones;during operation,the flow velocity should be reasonably controlled and the medium composition optimized;supplemented by measures such as coating protection and cathodic protection.Implementing prevention and control measures from the design source can significantly reduce the corrosion risk of the pump set and ensure the long-term safe and stable operation of the equipment.

Bonve pump always adheres to the philosophy of "Wholeheartedly Making Good Rotor Pumps," committed to providing global customers with customized conveying and mixing solutions. If you have technical inquiries, selection needs, case references, or other cooperation intentions related to Bonve rotor pumps, please feel free to contact us.  

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