Delo® XLI Corrosion Inhibitor – Concentrate
Delo® XLI Corrosion Inhibitor – Concentrate

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.

Typical Characteristics
Nitrate, amine, phosphate, borate, silicate
Specific gravity, 20°C, kg/l, ASTM D 1122
1.06 Typical
pH, ASTM D 1287
9.4 Typical
Storage stability
12 months if stored in non-opaque containers, 36 months if stored in opaque containers
Modified ASTM D1384 glassware corrosion tests
PASS (XLI 5% solution)
5% Dilution
Specific gravity, 20°C, kg/l, ASTM D 1122
1.00 Typical
pH, ASTM D 1287
8.1 Typical
Effect on non-metals, GME 60 255
No Effect
Hard water stability, VW PV 1426
No precipitate
Recommended Uses

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.

Delo® XLI Corrosion Inhibitor – Concentrate Is Recommended For Use In:

Detroit Diesel

Deutz TR0199-99-2091

GEC Alsthom Ruston

Liebherr MD 1-36-130 (DCA)


MAN 248

MAN Energy Solutions 2-stroke engines (operating with cooling water temperature below 100°C)

MAN Energy Solutions 4-stroke engines

MB 312.0

MTU 2000 & 4000 series engines


Newman-Haas Racing

Scania TI 2-98 0813 TB

Ulstein Bergen

Wärtsilä 32-9011 and ZBS0503



Performance Benefits

1. Environment

Delo XLI is based on low toxicity inhibitors and is readily biodegradable. The extended service life characteristic of this product reduces waste due to less frequent fluid disposal. The toxicological and environmental properties of Delo XLI were evaluated by an independent laboratory. The results are listed below: • LD50 >2000 mg/kg (Oral toxicity according to OECD Guideline No. 401) • LC50 >1000 mg/l (Fish toxicity according to OECD Guideline No. 203) • Biodegradability: 92% (18 days) (Test according to OECD Guideline No. 301E)

2. Corrosion Protection

Provides long-life protection against most forms of corrosion on the majority of metals including the aluminum heat transfer surfaces contained in modern engines.

3. Cavitation Protection

Offers cavitation protection without using nitrite or nitritebased supplemental coolant additives (SCAs).

4. Seal Compatibility

Has no adverse effect on rubber hoses and gasket materials as shown in testing a wide range of seal materials.

5. Heat Transfer Efficiency

The carboxylic acid inhibitor inhibitor forms a targeted mono-molecular protective layer on metal surfaces, thus providing efficient heat transfer.

6. Economics

Long life corrosion protection and low additive depletion often result in less maintenance and repair costs.