Delo® XLI Corrosion Inhibitor – Concentrate (Delo XLI) is a water-based, low toxicity, readily biodegradable, nitrite-free carboxylate inhibitor package. Based on patented Organic Additive Technology (OAT), Delo XLI provides long-life corrosion protection in aqueous solutions for all engine metals, including aluminum, iron, copper and solder alloys. Mixed with the appropriate amount of water, Delo XLI is recommended as a cooling water treatment. Delo XLI has been proven to provide effective protection for at least 32,000 hours in marine and stationary applications. It is compatible with glycol-based engine coolants.

Delo XLI can be used as an engine cooling water treatment, a flushing fluid, or a hot test fluid for new engine blocks. It is recommended for cooling water treatment operating below 100°C. For marine application the dosage may vary from 6.0–7.5% but a minimum of 5% volume of Delo XLI in water should be used. As an engine cooling water treatment, Delo XLI provides long-life corrosion protection. If Delo XLI is replenished regularly to compensate for leakage, the cooling water can be considered as fill for life. The use of soft water is preferred for dilution, though lab testing has shown that acceptable corrosion results are still obtained with water of 20°dH, containing not up to 500 ppm chlorides and 500 ppm sulphates.