Paint tanks are core equipment for storing coatings (such as paints, inks, and adhesives), and their corrosion resistance directly determines the quality of stored coatings (avoiding contamination, deterioration) and the service life of the tanks themselves. Coatings often contain solvents, resins, pigments, and additives—some of which (like strong solvents, acidic components) have strong chemical activity, making the tank body prone to corrosion if the material is improper. This article will systematically explain how to judge the corrosion resistance of paint tanks and analyze the differences in tank material requirements for storing different types of coatings.

I. How to Judge the Corrosion Resistance of Paint Tanks? 5 Practical Methods

The corrosion resistance of paint tanks cannot be judged by "appearance alone"; it needs to be comprehensively evaluated through material composition, surface treatment, performance testing, and actual application feedback. The following 5 methods can help you make an accurate judgment:

1. Check the "Material Composition" of the Tank Body—The Foundation of Corrosion Resistance

The inherent corrosion resistance of the tank body material is the core. Different materials have huge differences in resistance to chemical corrosion, so the first step is to confirm the material type and its composition:

• Common tank materials and their corrosion resistance bases:
  
  

• • Stainless steel (304/316/316L): The corrosion resistance comes from the chromium oxide passivation film on the surface. 304 stainless steel contains 18% chromium and 8% nickel, which can resist most neutral and weak acidic coatings; 316/316L adds molybdenum (2%–3%), which significantly improves resistance to chloride ion corrosion (suitable for coatings containing halogenated solvents, such as vinyl chloride-based paints). When judging, ask the manufacturer for the material test report (e.g., spectral analysis report) to confirm that the chromium, nickel, and molybdenum contents meet the standard (e.g., 316L requires ≥16% chromium, ≥10% nickel, ≥2% molybdenum).
    
    

• • Carbon steel with anti-corrosion coating: Carbon steel itself is prone to rust, so it must rely on surface coatings (e.g., epoxy resin, polyurethane, glass fiber reinforced plastic) for corrosion protection. To judge, check the coating type (epoxy resin is better for solvent-based coatings, polyurethane for water-based coatings) and thickness (the coating thickness should be ≥80 μm, measured by a coating thickness gauge—too thin will easily crack and peel).
    
    

• • Plastic (HDPE, PP, PVDF): Corrosion resistance comes from the chemical inertness of the polymer. HDPE and PP are suitable for neutral coatings, while PVDF (polyvinylidene fluoride) has excellent resistance to strong solvents and high temperatures (suitable for high-performance coatings like fluorocarbon paints). Judge by checking the material grade (e.g., "food-grade HDPE" is not enough; industrial-grade HDPE for coatings should have a density ≥0.95 g/cm³) and whether there are additives (e.g., anti-UV additives for outdoor storage).
    
    

• Red flags to avoid: Tanks made of "unknown alloy" (no material label), "recycled plastic" (with uneven color and impurities), or "thin-gauge carbon steel without coating"—these materials have poor inherent corrosion resistance and are prone to rust or dissolution when in contact with coatings.
  
  

2. Evaluate Surface Treatment Technology—Enhancing Corrosion Resistance

Even if the base material is good, improper surface treatment will reduce corrosion resistance. Focus on the following details:

• Stainless steel surface treatment:

• • Polishing grade: The surface should be polished to Ra ≤0.8 μm (mirror or brushed finish). A rough surface (Ra ＞1.6 μm) will have more micro-pores, where coating components can accumulate and cause localized corrosion (e.g., pitting). You can use a surface roughness tester to measure, or visually check for no obvious scratches, burrs, or oxidation spots.

• • Passivation treatment: After welding, stainless steel tanks need to undergo pickling and passivation (using nitric acid or citric acid solution) to repair the chromium oxide film damaged by welding. To judge, check if the weld area is as bright as the rest of the surface (no dark gray oxidation layers) and ask for a passivation test report (e.g., blue dot test—no blue dots indicate a complete passivation film).
    
    

• Plastic tank surface treatment:

• • Smoothness and integrity: The inner surface should be smooth, without mold marks, bubbles, or cracks. Cracks or bubbles will trap coating residues, leading to localized chemical reactions and material degradation. For example, a PP tank with a small inner bubble may absorb solvent from the coating, causing the bubble to expand and the tank wall to thin.
    
    

3. Conduct "Static Corrosion Testing"—Simulate Actual Storage Conditions

For key applications (e.g., storing high-value or highly corrosive coatings), it is necessary to conduct static corrosion testing to verify the tank’s resistance:

• Test method: Cut a sample of the tank material (same as the tank body), immerse it in the actual coating to be stored, seal it, and place it in an environment of 25°C (or the maximum storage temperature, e.g., 40°C for outdoor storage) for 7–30 days.
  
  

• Judgment criteria:

• • After immersion, the sample should have no obvious changes: no rust, no discoloration, no swelling (for plastic), no peeling (for coated carbon steel).

• • Test the coating quality after storage: If the coating stored with the sample has no turbidity, no color change, and no sediment (compared to the original coating), it means the tank material does not react with the coating.
    
    

• Example: When storing acidic coatings (e.g., water-based acrylic paint with pH 3–5), a 304 stainless steel sample immersed for 14 days should remain bright, and the paint should not turn yellow (yellowing indicates nickel dissolution from stainless steel).
  
  

4. Check Industry Certifications and Manufacturer Qualifications—Indirect Quality Guarantee

Certifications reflect whether the tank meets industry corrosion resistance standards. Focus on the following:

• Domestic certifications: GB/T 25198-2010《Stainless Steel Pressure Vessels for Storage》(for stainless steel tanks), HG/T 20698-2019《Technical Specifications for Glass Fiber Reinforced Plastic Tanks and Vessels》(for FRP tanks). Tanks with these certifications have passed corrosion resistance tests (e.g., salt spray test for stainless steel, solvent immersion test for FRP).
  
  

• International certifications: ASME BPE (for pharmaceutical/ food-grade coatings, requiring ultra-high corrosion resistance), ISO 12944 (for anti-corrosion coating systems on carbon steel tanks, specifying coating thickness and service life).
  
  

• Manufacturer qualifications: Choose manufacturers with "pressure vessel manufacturing licenses" or "special equipment manufacturing qualifications"—they have more standardized production processes (e.g., strict control of welding parameters for stainless steel tanks) to ensure corrosion resistance.
  
  

5. Refer to Actual Application Cases and User Feedback—Practical Verification

The most direct way to judge is to understand the tank’s performance in actual use:

• Ask for case studies: Ask the manufacturer to provide cases of the same tank model storing the same type of coating. For example, if you need to store solvent-based polyurethane paint, ask if there are customers who have used the tank for more than 2 years—if the feedback is "no tank corrosion, no paint deterioration," it means the corrosion resistance is reliable.
  
  

• User reviews: For commercial tanks (e.g., small plastic tanks for laboratories), check user reviews focusing on "whether the tank is corroded after long-term use" (e.g., "stored xylene-based paint for 6 months, no plastic deformation or solvent leakage").
  
  

II. Are There Differences in Tank Material Requirements for Different Coating Storage? Yes—Determined by Coating Composition

Coatings are divided into different types based on solvents, resin systems, and pH values, and their chemical activity varies greatly—this directly leads to different requirements for tank materials. Using the wrong material will cause tank corrosion, coating contamination, or even safety hazards (e.g., tank leakage). The following are the key requirements for common coating types:

1. Solvent-Based Coatings (e.g., Oil-Based Paints, Alkyd Paints)—Resist Strong Solvent Penetration

Solvent-based coatings contain a large amount of organic solvents (e.g., xylene, toluene, ethyl acetate), which have strong penetration and dissolution properties—they can swell plastic materials or dissolve the anti-corrosion coating on carbon steel. The material requirements are:

• Preferred materials:

• • 304/316 stainless steel: Stainless steel is chemically inert to most organic solvents and does not absorb solvents. 316 stainless steel is recommended for coatings containing halogenated solvents (e.g., chlorinated rubber paint) to avoid chloride ion corrosion.

• • PVDF plastic: PVDF has excellent solvent resistance (can resist xylene, acetone, etc.) and is suitable for small-capacity storage (e.g., laboratory samples).
    
    

• Materials to avoid:

• • Ordinary PP/HDPE plastic: These plastics absorb organic solvents easily—for example, HDPE immersed in xylene for 7 days will swell by 5%–10%, leading to tank wall thinning and leakage.

• • Carbon steel with ordinary epoxy coating: The solvent in the coating can dissolve the epoxy coating (especially low-quality epoxy), causing the coating to peel off and the carbon steel to rust. If carbon steel is used, it must be coated with solvent-resistant epoxy (e.g., bisphenol A epoxy with a thickness ≥120 μm) and tested for solvent resistance.
    
    

• Example: Storing oil-based wood paint (containing xylene) in a 304 stainless steel tank can ensure no solvent leakage or tank corrosion; using a PP tank will cause the tank to deform within 1 month.
  
  

2. Water-Based Coatings (e.g., Water-Based Acrylic Paints, Latex Paints)—Resist Water and pH Corrosion

Water-based coatings use water as the solvent, but they often contain pH regulators (e.g., ammonia water, organic acids) to adjust the pH to 7–9 (neutral to weakly alkaline) or 3–5 (weakly acidic). The main corrosion risks are "water-induced oxidation" (for metals) and "pH-induced chemical reaction" (for plastics). Material requirements:

• Preferred materials:

• • 304 stainless steel: Resists neutral and weakly alkaline water-based coatings. For weakly acidic water-based coatings (pH 3–5, e.g., water-based polyurethane paint), 316 stainless steel is better (to avoid chromium oxide film dissolution).

• • HDPE/PP plastic: These plastics are water-insoluble and stable to weakly acidic/alkaline environments. They are suitable for small to medium-capacity storage (e.g., 20L–200L tanks) and are cost-effective.

• • Carbon steel with polyurethane coating: Polyurethane coating has good water resistance and alkali resistance (better than epoxy for alkaline coatings). It is suitable for large-capacity storage (e.g., 1000L+ tanks) of weakly alkaline water-based coatings.
    
    

• Materials to avoid:

• • Ordinary carbon steel (no coating): Will rust quickly in water-based coatings—rust particles will contaminate the coating, causing it to turn brown and precipitate.

• • PVC plastic: PVC is unstable in weakly alkaline environments (pH ＞8) and will release plasticizers, leading to coating contamination and tank brittleness.
    
    

• Example: Storing weakly alkaline water-based latex paint (pH 8–9) in an HDPE tank is safe and cost-effective; using a PVC tank will cause the tank to become brittle and leak after 3 months.
  
  

3. High-Corrosion Coatings (Acidic/Alkaline Coatings, High-Solid Coatings)—Special Material Requirements

Some special coatings have strong corrosion, requiring tanks with "enhanced corrosion resistance":

• Acidic coatings (pH ＜3, e.g., phosphating primer, acidic rust-inhibiting paint):

• • Preferred materials: 316L stainless steel (with molybdenum, resistant to acid corrosion), PVDF plastic, or glass fiber reinforced plastic (FRP) with vinyl ester resin (resistant to strong acids).

• • Taboo: 304 stainless steel (acid will dissolve the chromium oxide film, causing pitting), ordinary plastic (PP/HDPE will be corroded by strong acid, causing material decomposition).
    
    

• Alkaline coatings (pH ＞10, e.g., alkaline zinc-rich primer):

• • Preferred materials: HDPE/PP plastic (stable to strong alkali), FRP with epoxy resin (alkali-resistant), or 316 stainless steel (resistant to weak alkali; for strong alkali, plastic is better).

• • Taboo: Carbon steel (even with coating—strong alkali will peel off the coating and corrode the steel), PVC plastic (strong alkali will decompose PVC).
    
    

• High-solid coatings (solid content ＞70%, e.g., high-solid epoxy paint):

• • Preferred materials: 304/316 stainless steel (high-solid coatings have high viscosity and are not easy to clean—stainless steel is smooth and easy to clean, avoiding coating residue and localized corrosion).

• • Taboo: Plastic tanks with rough inner surfaces (residue will accumulate in micro-pores, causing long-term chemical reactions and material degradation).
    
    

4. Special-Function Coatings (e.g., Heat-Resistant Coatings, Conductive Coatings)—Consider Temperature and Additive Corrosion

• Heat-resistant coatings (used at 150–300°C, e.g., silicone heat-resistant paint):

• • Preferred materials: 316 stainless steel (resists high-temperature oxidation), carbon steel with high-temperature resistant coating (e.g., ceramic coating, resistant to 300°C+).

• • Taboo: Plastic tanks (most plastics soften or decompose at 100°C+).
    
    

• Conductive coatings (containing metal powders, e.g., copper powder conductive paint):

• • Preferred materials: 304 stainless steel (metal powder will not react with stainless steel; plastic tanks may generate static electricity, but conductive coatings themselves are anti-static—plastic is also optional, but stainless steel is more durable).

• • Note: Avoid using carbon steel (metal powder in the coating may form a galvanic cell with carbon steel, accelerating steel corrosion).
    
    

III. Key Precautions for Using Paint Tanks to Maintain Corrosion Resistance

Even with the right material, improper use will reduce corrosion resistance. Pay attention to the following:

1. Avoid "Cross-Storage" of Different Coatings: Do not use the same tank to store different types of coatings (e.g., switching from solvent-based paint to acidic paint) without thorough cleaning. Residues from the previous coating will react with the new coating or the tank material, causing corrosion. For example, solvent residues from oil-based paint will dissolve the polyurethane coating on a carbon steel tank when storing water-based paint.
   
   

2. Control Storage Temperature: High temperatures accelerate chemical reactions—for example, storing solvent-based coatings in a stainless steel tank at 50°C+ will increase solvent volatility, leading to higher internal pressure and potential damage to the tank’s welds. The recommended storage temperature is 5–35°C.
   
   

3. Regular Inspection and Maintenance:

• Stainless steel tanks: Check for pitting or rust monthly (especially weld areas). If found, use a stainless steel wire brush to remove rust, then apply passivation solution to repair the passivation film.

• Plastic tanks: Check for swelling, deformation, or cracks quarterly. Replace immediately if any of these occur (plastic damage is irreversible).

• Coated carbon steel tanks: Check for coating peeling or bubbling. If peeling is found, remove the old coating, sand the steel surface, and reapply anti-corrosion coating.
  
  

4. Empty the Tank When Not in Use: Long-term storage of empty tanks (especially in humid environments) will cause corrosion—for example, an empty carbon steel tank will rust due to moisture in the air. After use, clean the tank thoroughly, dry it, and seal it with a dust cover.
   
   

Judging the corrosion resistance of paint tanks requires a combination of material composition, surface treatment, performance testing, certifications, and practical cases—only by checking these aspects comprehensively can you avoid choosing tanks with poor corrosion resistance. Meanwhile, different coatings have distinct chemical properties: solvent-based coatings require solvent-resistant materials (stainless steel, PVDF), water-based coatings need water and pH-resistant materials (stainless steel, HDPE), and high-corrosion coatings (acidic/alkaline) demand enhanced corrosion-resistant materials (316L stainless steel, FRP).

By matching the tank material to the coating type and following proper use and maintenance methods, you can ensure the tank’s long service life and the quality of the stored coatings. If you have special coating storage needs (e.g., ultra-high temperature, strong acid), it is recommended to customize tanks with manufacturers and conduct pre-use corrosion testing to avoid risks.