Houghton Chemical Corporation Scale and Corrosion Inhibitors - Belclene 494

BelcleneŽ 494 is a unique water treatment additive which has both deposit and corrosion control properties. It can therefore be used as a basic building block for a wide range of cooling water formulations used across the spectrum of water chemistries. This Waterfront discusses the corrosion inhibition properties of Belclene 494.

Mechanism
Belclene 494 is a phosphonocarboxylic copolymer (POCA) with both sulphonate and phosphonate functionality. The phosphonate function is primarily responsible for the corrosion inhibiting properties of the molecule. Tafel polarisation scans have been generated for the product and the curves, produced in a 300mg/l Ca (as Ca2+) water at pH 8, are shown in figure 1

The scans clearly show a shift in the anodic range indicating that Belclene 494 is inhibiting the corrosion process at the anode. This is a significant difference from most other phosphonates, which offer only limited cathodic inhibition.

When Belclene 494 is combined with cathodic inhibitors it can be expected to significantly boost the overall corrosion performance of the formulation.

Performance testing
The performance of Belclene 494 has been assessed as a corrosion inhibitor in a rotating coupon test, which evaluates corrosion control performance under dynamic test conditions, and the results are given in table 2.

Conditions of test
Rotating coupon test at 40°C		Chloride: 200 mg/l
Dose level of additive: 50 mg/l (derives)		Sulphate: 200 mg/l
Ca²⁺:15O mg/l as CaCO₃		pH : 8.1
Total hardness: 225 mg/l as CaCO₃
Total alkalinity: 225 mg/l as CaCO₃

Table 2: Corrosion inhibition results
Additive	Corrosion rate (mpy)
PBTC	3.1
sulphonated terpolymer	>5
BelcorŽ 575	0.8
Belclene 494	1.9

Belclene 494 has been optimised to give maximum scale control performance, but with additional corrosion control properties. Belcor 575 corrosion inhibitor is recognised within the industry as the most effective corrosion inhibitor of its kind. Although Belclene 494 does not match the performance of Belcor 575 it is clearly shown to have corrosion inhibiting properties which phosphonates such as PBTC and sulphonated polymers do not have.

Combined with its wide range of scale control properties, Belclene 494 can offer a complete scale and corrosion control package and can be used as a basic building block for many cooling water formulations.

Warranty - Patent Position
The information contained herein is, to our knowledge, true and accurate. Because conditions of use are beyond our control, we make no warranty or representation, express or implied. except that the products discussed herein conform to the chemical descriptions shown on the labels. Nothing contained herein should be construed as permission or recommendation to infringe any patent. No agent, representative or employee of this company is authorised to vary any terms of this notice.