Extension of the application of Belcor® 575 corrosion inhibitor into halogenated cooling systems

Belcor 575 corrosion inhibitor is a unique, high performance additive for the prevention of corrosion of mild steel in cooling systems. It is a versatile building block for all-organic formulations, and is a forgiving product which readily recovers from system upsets. It is an environmentally acceptable corrosion inhibitor and has a good biodegradabilty profile. The use of Belcor 575 has until now been limited to systems with low level continuous or shock halogenation. Exposure to high level, continuous chlorination resulted in impaired performance. A cost-effective method has now been developed to allow Belcor 575 to be used in halogenated cooling systems.

Extensive pilot cooling tower studies in FMC laboratories in Manchester, England, and Princeton, New Jersey, have shown that the formulation of Belcor 575 with monoethanolamine (MEA) at a fixed ratio of 3:1 (as solids) allows Belcor 575 to give excellent corrosion control in halogenated waters. It has been suggested that MEA forms a haloamine complex with the halogen and that this complex reduces the reversion of Belcor 575 to orthophosphate.

In the pilot cooling tower studies, the blend of Belcor 575 and MEA was added to the system. A daily shock dose of halogen was added to achieve a residual of 0.2 ppm to 1.0 ppm free halogen. The orthophosphate content of the recirculating water was measured to assess the reversion of the Belcor 575. The results shown in figure 1 confirm that Belcor 575 formulated with MEA gave much better stability to the oxidising biocide.

Table 1 confirms that the excellent corrosion inhibition properties of Belcor 575 are maintained when Belcor 575 is formulated with MEA. Further tests (see figure 2) show that the blend of Belcor 575 and MEA has no detrimental effect on the biocidal activity of halogen-based oxidising biocides.

Monoethanolamine is a readily available, low cost commodity chemical. It is used in a typical all-organic formulation at about 2%, and therefore adds little to the cost of the formulated product. It is compatible with other components of proprietary formulations and remains stable across a broad pH range.

Figure 1: Reversion to orthophosphate - comparison of Belcor 575 and Belcor 575 with MEA Process simulation test results

Conditions of test
Calcium		300 ppm as CaCO3
Magnesium		150 ppm as CaCO3
Alkalinity		100 ppm as CaCO3
pH		8-8.5
Temperature		40°C
Heat flux		31 kW/m2 (10 000 BTU/ft2/hr)
Half life		18 hours
Flow rate		0.9 m/s (3 ft/s)

Table 1: Corrosion rates from process simulation tests on Belcor 575 with MEA and Belcor 575 with BCDMH

Test formulation (ppm solids)		Corrosion rate mpy*		Deposition rate mcy*
12 ppm Belcor 575 + 4 ppm MEA with 20 ppm BCDMH		1.4		36.5
12 ppm Belcor 575 with 20 ppm BCDMH		2.2		36.5

Figure 2 :Effect of Belcor 575 with MEA on biocidal activity

Test conditions
Water chemistry
Basle tap water (200 ppm calcium hardness)

Dose
Belcor 575 20 ppm (solids)
MEA 6 ppm (solids)
BCDMH 10 ppm total halogen

Bacteria (mixed culture)
Bacillus subtilis
Pseudomonas fluorescens

Benefits to the user

• Belcor 575 is already the best available corrosion inhibitor for use in all-organic formulations as it gives significantly better performance than "commodity" phosphonates such as HEDP. Reduced iron fouling, improved plant integrity and maintenance all contribute to a positive payback on the cost of Belcor 575 in comparison with HEDP.
  
  
• Belcor 575 is effective in systems with well controlled, low level halogenation. End users should continue to focus on achieving such control and perhaps utilise techniques such as oxidation-reduction potential (ORP) monitoring. However, a cost-effective method has been developed to allow the benefits of Belcor 575 to be applied to systems where halogen control is poor.
  
  
• Belcor 575 is formulated with monoethanolamine (MEA) to inhibit reversion of Belcor 575 to orthophosphate. MEA is a low cost, readily available raw material which can be incorporated in most proprietary formulations.
  
  
• The value of the performance to the end user, in terms of reduced potential for fouling, improved heat transfer efficiency and enhanced system integrity more than justifies the slightly higher formulation cost.
  
  
• Belcor 575 in formulation with MEA complies with regulations on industrial discharge and hence is an environmentally acceptable alternative to chromate.

Process Additives Division