Use of METALGUARD SCA80 as a Supplemental Coolant Additive for Heavy-Duty Diesel Engines

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METALGUARD SCA80 is a high-nitrite supplemental coolant additive for use in heavy-duty diesel engines requiring a precharged fully-formulated antifreeze meeting ASTM D 6210, TMC of ATA RP329/330, Caterpillar EC-1, etc. METALGUARD SCA80 is added to the coolant in an engine to maintain the levels of depletable corrosion inhibitors and other critical additives in effective/acceptable ranges. Some inhibitors, including nitrites, nitrates, silicates and MBT/tolyriazoles are converted into inactive compounds relative to corrosion protection as they perform their function of protecting engine metals, and must be boosted at intervals that depend upon engine operating conditions and hours of operation at various loading levels.

The best way to determine when to add a supplemental coolant additive which contains these depletable antifreeze/coolant ingredients is to measure the concentrations of the depletable components in your antifreeze and add each based on these analyses. However, this is not a practical approach, because it is costly and requires significant analysis time at a qualified laboratory. A method that is commonly employed and practical is to measure the level of a "marker" inhibitor and add SCA when its level falls below a certain point. This "marker" inhibitor is the one that depletes to levels of inadequate protection most rapidly. If you keep this ingredient of the antifreeze within acceptable bounds, the other depletable additives will theoretically always remain above minimum acceptable levels.

In precharged antifreeze containing elevated levels of nitrite, nitrite is the most appropriate “marker.” It can be checked quickly and with sufficient accuracy in the field with approved test strips or test kits. When these test methods indicate nitrite levels below 800-1000ppm, it is then time to add METALGUARD SCA80 per the following schedule:

Measured Nitrite Level	Add this much METALGUARD SCA80 per 4 gallons of system cooling capacity @ 50/50
1000	0.6 ounce
800	0.8 ounces
500	1.5 ounces
0	2.5 ounces

Many companies add supplemental coolant additives based on a set elapsed operating time or mileage at standard operating conditions. Many add SCA to a heavy-duty engine cooling system at approximate intervals of 12,000-18,000 miles, 225-275 hours of operation, or 3 months of operation. The best way to determine your recommended mileage or time intervals is to accumulate operating data while using the strips or kits. These data will allow you to establish statistically valid SCA addition intervals based upon the time or mileage over which nitrite/molybdate levels fall to recommended minimums.

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Version date: December 5, 2011
Supersedes: July 14, 2011