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MAR-71™ is a very effective biocide, used to prevent and combat microbiological growth in closed cooling water systems as well as in lubricating oil systems.

Product information

Bacteria are the cause of many corrosion problems, as while they grow, they produce a variety of acids and in some cases slimy layers on metal surfaces which results in reduced heat transfer and corrosion in bearings. Nitrites, Phosphates and emulsifying oils are good nutrient media for bacteria. MAR-71™ has proven to be a very effective disinfectant. Lower dosages of MAR-71™ can also be used to prevent infection.


  • Kills micro-organisms in closed cooling water systems and lubrication oil systems
  • Prevents corrosion caused by microorganisms
  • No cases have been reported where bacteria have become immune to MAR-71
  • Biodegradable, does not accumulate in the environment
  • HOCNF registered for use in the North Sea Offshore sector, yellow/gold classification


  • One product, two different applications


Physical properties

Appearance Colourless to yellow
Density [g/ml] 1.06
Form Liquid
pH 10 in 0.15% solution

Technical data

Solubility in water Totally soluble


  • Approved by The Norwegian Food Safety Authority



Directions for use

Closed cooling water circuits Especially when berthing for a longer period in harbours in warmer climates, the risk of infection of the cooling water systems with microorganisms is considerable. When this happens, acids are formed and at the same time, the corrosion inhibitors present in the system will be eaten away by the bacteria creating corrosive conditions. Regular testing for the presence of bacteria in the cooling water by the use of "dip slides" is therefore strongly recommended. Between 0.5 and 1.5 litres/ton. MAR-71 should be added to contaminated systems. The system should be circulated for three days after which the complete contents of the cooling system is dumped. Before refilling the system with (distilled) water and the initial dosage of Dieselguard or Rocor NB Liquid, the system should be thoroughly flushed with fresh water. It is recommended to re-test for the presence of bacteria after the system has been in operation for 24 hours. The described procedure is to be repeated if necessary. For heavily contaminated systems and systems contaminated with scale/oil, it is recommended to acid clean and/or degrease the system prior to disinfecting

Caution: During disinfecting, evaporators and other equipment which use cooling water and which are used in connection with the production of drinking water are not to be used.

Lubricating oils The presence of water in lubricating oil, either caused by condensation or by leakage of cooling water, provides excellent growing conditions for micro-organisms in lube oil systems. The presence of bacteria will cause changes in lube oil characteristics, cause corrosion, water emulsion and clogging of filters. Regular control and necessary action to combat bacteriological contamination can avoid above mentioned problems. The recommended decontamination procedure is as follows:
1. Transfer 80-90% of the lubricating oil into a renovation tank and heat to 85-95°C while separating for 12 hours. Continue heating for another 12 hours without separating. 2. To the remaining oil in the sump-tank, between 0.5 and 1 litres/ton MAR-71 is added. Circulate the contents of the sump-tank for 12-24 hours. Note that during circulation, filters may get clogged by dead microorganisms. Special observation of filters, and if necessary, cleaning of same, is therefore required. 3. Empty and clean the sump-tank. 4. Transfer the circulating oil from the renovation tank back into the sump-tank and fill with fresh oil. As an alternative to the above procedure, increase of the bacteriological contamination can be stopped by adding 0.3 - 0.5 litres/ton MAR-71 to the lubrication oil. At a later stage, proper disinfecting must follow.

Note: Please check with the lubrication oil manufacturer regarding dosage rates for your brand of oil. In case bacteriological contamination occurs and has already caused corrosion, the lubrication oil must be fully exchanged. Consult lubrication oil manufacturer. Before refilling the system, it is highly recommended to rinse the system for 24 hours with flushing oil to which 0.5 - 1 litres/ton MAR-71 is added. This procedure and the addition of 0.1 - 0.5 litres/ton MAR-71 to the new oil will prevent re-infection of the lubricating oil.