Corrosion Prevention Construction Plan for Stainless Steel Storage Tanks in Breweries

I. Paint System Specifications:

Stainless Steel Tank Interior Anti-Corrosion Process:
Anti-corrosion lifespan: 10 years

II. Photographs of On-Site Corrosion Severity:

III. On-site Situation Description:

1. The client's site utilizes stainless steel storage tanks fabricated from welded stainless steel plates. The longest operational lifespan recorded is 26 years. Due to the use of welding rods with lower grade than the steel plates, severe corrosion is concentrated at the weld points. Pinholes have also appeared. Individual steel plates exhibit rust and pinholes.
2. The tank bottom and discharge port exhibit severe corrosion. This is caused by excessive NaCl precipitation during production damaging the tank bottom, compounded by frequent discharge at the outlet, leading to severe corrosion. Internal coating must be applied during this process to prevent future issues where internal coating becomes impossible after elbow replacement.
3. The tank walls have a thickness of 4-5mm. After a period of use and corrosion, the walls have thinned further. What treatment should be applied after sandblasting.
4. Existing tanks already have pinholes. After internal coating, is external coating also required.

IV. Construction Process

1. Substrate Preparation
Prior to coating, rust removal on the stainless steel tank interior surface must be performed using various methods: dry sandblasting, wet sandblasting, or grinding. The surface must achieve ≥ Sa2.5 grade per ISO 8501-1-1998 standards, with a roughness of 40–75 μm. The tank surface must be free of oxide layers and adhering contaminants.
If pinholes or leaks are present in the storage tank, the tank wall near the pinhole must be thoroughly cleaned and the oxide layer removed. Since pinholes are through-holes, cleaning is required not only on the inner wall side but also on the outer wall simultaneously.

2. Tank Cleaning
After substrate preparation, the tank interior must be thoroughly cleaned prior to coating. Any dust or iron filings adhering to the walls during rust removal will compromise coating effectiveness.
For optimal corrosion protection, the inner surface of the tank top must also be sanded. Cleaning proceeds from top to bottom. If severe corrosion is present at the discharge port, a replacement plan must be prepared in advance. Replacement and welding of these sections should occur during the tank cleaning phase.

3. Putty Repair + Pre-Coating
After sanding, pinholes and defects on the tank surface become visible. Use epoxy sealing putty to fill and level pinholes and substrate imperfections. For pinholes with through-holes, seal both the inner and outer walls simultaneously.
For hard-to-reach areas like weld seams and corners, apply primer in advance before formal primer application. Carefully coat these areas with primer to ensure no missed spots. After priming, wait 4 hours before starting formal primer application.

4. Primer and Topcoat Application
After putty repair and pre-coating, apply acid-alkali primer to the tank's inner wall. Apply one coat of primer with a thickness of 50μm. The primer enhances adhesion between the stainless steel tank body and the topcoat, preventing paint film peeling. Allow the primer to cure for 24 hours with adequate ventilation before applying the topcoat.
After 24 hours of primer curing, apply the first coat of topcoat. Apply the second coat of topcoat 24 hours after the first coat. After 24 hours of the second topcoat application, apply the third topcoat.
After completing all three topcoats, ventilate the tank for 48 hours to dry.
Before each coat application, clean the previous paint film surface. Remove dust with a dry cloth or brush.

5. Film Thickness Inspection
After completing the topcoat application and allowing 48 hours of drying, personnel shall enter the tank for non-destructive testing (NDT) and film thickness measurement. If any area fails to achieve a dry film thickness of 450μm or exhibits unsealed damage, touch-up coating and repair must be performed promptly. Following touch-up, allow another 48 hours of drying before re-conducting NDT and thickness measurement on the tank.

6. Tank Maintenance
After non-destructive testing confirms the coating meets requirements, continue ventilating and drying the tank. Maintain drying for 24 hours × 5 days. If recoating or reprocessing occurs, recalculate drying time; total required drying is 24 hours × 7 days.

7. Water Storage Test
After completing the 7-day curing period, perform a water storage test on the tank coating. Fill the tank completely with water and immerse it for 48 hours. If no leaks occur and the coating shows no abnormalities, this indicates successful on-site construction meeting usage requirements. After draining all accumulated water, the tank may be used for production.