Rapid Nitrite Depletion in Modern Excavator Cooling Systems: Causes and Solutions

Overview

Modern excavators equipped with Controlled Atmosphere Brazing (CAB) aluminum radiators and cooling systems have introduced new challenges for coolant chemistry. One of the most common issues is rapid nitrite depletion when using conventional nitrited coolants.

What Causes Rapid Nitrite Depletion?

The problem stems from a chemical reaction between the coolant’s nitrites and unprotected aluminum surfaces in CAB-brazed components. While this reaction does not have a formal name, it is essentially a form of aluminum corrosion or oxidation.

Industry professionals typically describe the issue by its cause or its effects:

• Reaction with CAB aluminum/flux
• Rapid nitrite depletion
• Aluminum corrosion/pitting
• White residue or precipitate formation

This reaction:

• Consumes nitrites quickly
• Can form precipitates that clog the cooling system, leading to overheating
• May increase coolant pH
• Often produces an ammonia-like odor, which is a common symptom

Why Does This Matter?

Nitrites are critical for protecting against liner pitting and cavitation in heavy-duty engines. When nitrites are depleted prematurely, the system loses this protection, increasing the risk of engine damage and costly downtime.

Recommended Solution

To prevent rapid nitrite depletion and associated issues:

• Flush the cooling system thoroughly before introducing new coolant.
• Use a coolant formulated for modern aluminum systems, specifically those compatible with CAB-brazed components.

For users already relying on Chevron products, Chevron Delo ELC Advanced Antifreeze/Coolant is recommended. This nitrited organic additive technology (NOAT) formulation is engineered with anti-reaction chemistry to:

• Prevent nitrite depletion
• Protect CAB-brazed aluminum
• Maintain long-life performance

Key Takeaways

• Rapid nitrite depletion is a corrosion-driven reaction between nitrites and unpassivated aluminum surfaces.
• Symptoms include white residue, overheating, increased pH, and ammonia odor.
• The best defense is proper system flushing and using a CAB-compatible coolant like Chevron Delo ELC Advanced.

Case Study

Background

• Customer: Canadian open-pit gold and silver mine
• Equipment: Caterpillar 6040 Excavator
• Component: Radiator LH
• Coolant Used: Chevron Delo Extended Life Coolant (ELC) 50/50 premix
• Sample Date: October 2025
• Lab Report: Fluid Life Corporation

Modern excavators increasingly use Controlled Atmosphere Brazing (CAB) aluminum radiators and cooling components for improved thermal efficiency and weight reduction. However, these systems introduce unique chemical compatibility challenges with traditional nitrited coolants.

Problem

The coolant analysis revealed:

• Nitrite levels dropped from 690 ppm to 267 ppm within a short service interval.
• pH increased from 8.20 to 9.27, indicating a chemical imbalance.
• Trace precipitate observed, though no magnetic particles.
• Coolant pH is trending up rather than down
• Rapid nitrite depletion compromises corrosion protection for iron and steel.
• Precipitate formation risks clogging passages, reducing heat transfer and causing overheating.
• Elevated pH and potential ammonia odor suggest ongoing chemical reaction.

Root Cause

A chemical reaction between nitrites in the coolant and unpassivated aluminum surfaces in CAB-brazed components:

• Nitrites oxidize on aluminum, forming insoluble compounds.
• This reaction accelerates nitrite consumption and can produce ammonia as a byproduct.
• Resulting precipitates may appear as white residue in the system.

Industry does not assign a formal name to this reaction; it is generally described as aluminum corrosion/pitting due to nitrite interaction.

Consequences

• Loss of corrosion inhibitors → Increased risk of cavitation and pitting.
• Formation of deposits → Reduced cooling efficiency → Overheating.
• Potential odor and pH imbalance → Indicator of ongoing chemical instability.

Solution

1. Flush the cooling system thoroughly to remove residual contaminants and precipitates.
2. Switch to a coolant formulated for CAB aluminum systems, such as:
   • Chevron Delo ELC Advanced Antifreeze/Coolant (NOAT)
     • Nitrited Organic Additive Technology with anti-reaction chemistry.
     • Compatible with CAB-brazed aluminum, preventing nitrite depletion.
3. Monitor nitrite levels and pH regularly during initial service intervals.
4. Avoid mixing coolant types to prevent additive incompatibility.

Lessons Learned

• Modern aluminum cooling systems require chemically compatible coolants.
• Routine coolant analysis is critical for early detection of additive depletion.
• OEM and coolant manufacturer guidelines should be strictly followed for coolant selection.