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How can evaporators prevent salt corrosion in seawater desalination systems?
2026-04-10
As a professional manufacturer specializing in evaporator equipment, Jiangsu Zongheng Concentration and Drying Equipment Co., Ltd. would like to share our practical experience in salt corrosion prevention for seawater desalination evaporators today. Serving as the core component of the entire seawater desalination system, evaporators are constantly exposed to high-salinity seawater and corrosive chloride ions during long-term operation. Uncontrolled salt corrosion will directly shorten equipment service life, increase operating costs and even trigger unplanned system shutdowns.
Based on years of on-site project delivery and equipment operation data, we have summarized four core practical solutions to curb salt corrosion of evaporators, covering material selection, structural design, operational process control and daily equipment maintenance.
Selection of Targeted Corrosion-Resistant Materials
Seawater features high chloride ion concentration and strong corrosiveness, so the material selection of evaporator main structures needs to give top priority to corrosion resistance and structural strength. In our actual engineering projects, we mainly adopt three mature metal materials: 316L stainless steel, 2205 duplex stainless steel and pure titanium.
Titanium material stands out thanks to its ability to generate a compact and stable oxide protective film on the metal surface, which delivers outstanding resistance against continuous chloride ion erosion. 2205 duplex stainless steel, with rationally optimized chromium and molybdenum composition, shows great performance in resisting pitting corrosion and crevice corrosion in high-salinity working scenarios.
To balance anti-corrosion performance and overall project cost, we adopt composite structural designs for vulnerable high-corrosion positions including welding seams and tube sheet joints. We match carbon steel base materials with professional anti-corrosion coatings or stainless steel linings for these key parts, which cuts down overall equipment manufacturing cost without compromising long-term anti-corrosion effects.
Optimized Structural Design to Avoid Localized Corrosion Risks
Most evaporator corrosion failures in actual operation stem from unreasonable structural design rather than raw material defects. We optimize equipment structures to eliminate hidden corrosion risks from the design stage.
First, we properly enlarge the cylinder diameter and rearrange the layout of heat exchange tubes. This design adjustment reduces fluid flow resistance inside the equipment and eliminates dead flow zones, effectively avoiding salt crystal accumulation that induces under-deposit corrosion. Second, we replace conventional welding processes with roller welding for core connecting parts. This method prevents intergranular corrosion and structural strength decline in the welding heat-affected zone, a common flaw of traditional welding technology.
Besides, we equip each stage of multi-effect evaporators with independent salt mist separation devices. These devices block high-salinity steam from entering downstream equipment and avoid cross-stage steam corrosion. For joints between tube sheets and heat exchange tubes, we apply integrated expansion and welding technology to improve overall sealing performance and eradicate crevice corrosion hidden in tiny gaps.
Precise On-site Process Control to Reduce Corrosion Sources
Corrosion speed can be effectively controlled by stabilizing operating parameters and improving incoming water quality. We standardize three sets of process control specifications for seawater desalination evaporator operation.
Seawater Pretreatment
Hardness ions (calcium and magnesium ions) and suspended solids in raw seawater will cause scaling on heat exchange tube walls. Scaling not only reduces heat exchange efficiency, but also accelerates local under-deposit corrosion. We adopt combined softening and filtration processes to remove impurities in advance, lowering both scaling risk and the concentration of free corrosive ions in seawater.
Temperature and Flow Rate Regulation
Local overheating will greatly accelerate electrochemical corrosion inside metal equipment. We match adaptive flow distribution systems to ensure steady and uniform seawater flow velocity inside all heat exchange tubes, avoiding partial overheating and salt sedimentation caused by uneven fluid flow.
Deep Deaeration Treatment
Dissolved oxygen and carbon dioxide in seawater are key drivers of electrochemical corrosion. We conduct strict deaeration and decarbonization treatment for incoming seawater. In practical operation of multi-stage flash distillation evaporators, we control dissolved oxygen content below 20 ppb and carbon dioxide content below 3 ppm to minimize electrochemical corrosion reactions.
Standardized Daily Maintenance and Anti-Corrosion Management
Perfect design and high-quality materials cannot eliminate corrosion risks completely, so regular and standardized daily maintenance is indispensable for long-term stable operation of evaporators.
Regular cleaning is arranged periodically: we choose targeted cleaning methods based on actual salt deposition conditions, including chemical cleaning with citric acid and EDTA solutions, as well as physical high-pressure water jet cleaning. Timely removal of salt dirt and residues on inner walls can completely avoid under-deposit corrosion.
We also carry out regular full inspection of anti-corrosion coatings on carbon steel components. Once coating peeling or damage is found, we conduct immediate repair. Our matched epoxy resin coatings and organic amine-cured coatings can steadily adapt to long-term working conditions with 7% salinity and 120℃ medium temperature, with a service life of more than 5 years.
Moreover, we install zinc-based and aluminum-based sacrificial anodes at vulnerable positions such as welding seams and bolt connection points. Relying on electrochemical cathodic protection, these anodes preferentially corrode to protect the metal base of evaporator equipment, forming a reliable passive anti-corrosion barrier for key weak parts.
Salt corrosion prevention for seawater desalination evaporators is a systematic project covering design, production, operation and maintenance. Only by combining optimized materials, reasonable structure, precise process control and full-cycle maintenance can enterprises cut equipment failure rates and extend the overall service life of desalination evaporators to the maximum extent.