Restoring a Rusted Diesel Fuel Tank: Methods, Materials, and Field Wisdom

[MikePhua]

Understanding Rust Formation in Diesel Tanks
Rust in diesel fuel tanks is primarily caused by prolonged exposure to moisture and oxygen. Condensation inside partially filled tanks accelerates corrosion, especially in older steel tanks like those found on Case 310F dozers. Over time, rust flakes can clog fuel filters, damage injectors, and compromise engine performance.
Terminology Notes

• Sediment Bowl: A catchment chamber at the tank’s base that collects debris and water.
  
• Naval Jelly: A phosphoric acid-based gel used to dissolve rust.
  
• Electrolysis: A chemical process using electrical current to transfer rust from steel to a sacrificial metal.
  
• Tank Coating: A fuel-resistant sealant applied to the interior of a tank to prevent future corrosion.
  
• Pickling: A method of rust removal using strong acids to clean metal surfaces.
  

Initial Cleaning and Inspection
The first step is to remove loose rust and debris. This can be done by:

• Draining the tank completely
  
• Removing the sediment bowl and flushing with a pressure washer
  
• Inspecting the tank interior via the fill hole or access ports
  
• Spraying diesel fuel inside after washing to prevent flash rust
  

One operator noted that even after pressure washing, caked rust remained unreachable under the seat area of the tank. This highlights the challenge of cleaning complex tank geometries.
Rust Removal Techniques
Several methods have proven effective depending on tank size and access:

• Vinegar Soak: White or apple cider vinegar can dissolve surface rust. Fill the tank and let it sit for several days, rotating periodically.
  
• Mechanical Agitation: Add sharp gravel, nuts, bolts, or chain segments to the tank with fluid and shake or rotate to dislodge rust.
  
• Electrolysis: Insert a steel rod and apply current to transfer rust to the rod. This method is slow but effective for deep rust.
  
• Acid Treatment: Muriatic acid or phosphoric acid can strip rust but must be neutralized afterward with baking soda or acetone.
  
• Naval Jelly: Effective for spot treatment but impractical for large tanks due to cost and coverage limitations.
  

Coating the Tank Interior
Once rust is removed, applying a protective coating can prevent future corrosion. Popular products include:

• POR-15: A fuel-resistant sealant that plugs pinholes and adheres to cleaned metal
  
• Red Kote: A rubbery coating that seals rust and prevents flaking
  
• Kreem: Often used in motorcycle tanks, requires thorough prep and drying
  

Application tips:

• Ensure the tank is completely dry before coating
  
• Rotate the tank to ensure even coverage
  
• Use compressed air or bore scopes to inspect hard-to-reach areas
  
• Seal fittings and apply light air pressure to test for leaks after curing
  

Field Anecdotes and Practical Wisdom
One mechanic shared a story of cutting open the bottom of a tank to access rusted areas, then welding in a new plate. While effective, this method requires skill and caution due to diesel fumes. Another technician used a rotisserie-style table to slowly rotate the tank with gravel and cleaner inside—an approach borrowed from radiator shops.
A retired engineer recalled restoring a Unimog tank with over 50 pinholes using POR-15 and JB Weld. The tank held up for years without leaks, proving that even severely damaged tanks can be salvaged with the right materials.
Preventive Measures

• Keep tanks full to minimize condensation
  
• Use fuel stabilizers and biocides to prevent microbial growth
  
• Drain water from sediment bowls regularly
  
• Replace corroded caps and seals to prevent moisture ingress
  
• Store equipment in dry conditions when idle
  

Historical Context and Design Considerations
Older dozers like the Case 310F often integrate the fuel tank into the seat assembly, complicating access and cleaning. Modern designs favor modular tanks with built-in drains and inspection ports. The evolution reflects a shift toward serviceability and corrosion prevention.
Conclusion: From Rust to Reliability
Restoring a rusted diesel tank is a labor-intensive but rewarding process. Whether using vinegar, electrolysis, or industrial coatings, the goal is the same: a clean, sealed tank that won’t sabotage your fuel system. With patience, creativity, and a few field-tested tricks, even the most stubborn rust can be defeated. As one operator put it, “It’s not just about cleaning metal—it’s about keeping the heart of the machine beating.”