ABSTRACT

Polyaspartates have been compared to phosphonates and polyacrylates in order to evaluate their efficiency as corrosion and calcium carbonate scale inhibitors and also as dispersive agents. This evaluation shows that polyaspartates may be considered as multifunctional inhibitors. Microvision experiments confirm nevertheless that they have some similitudes of action with polyacrylates particularly concerning scale inhibition and protective film formation.

INTRODUCTION

More and more severe environmental constraints have prompted users to assume a rational management of industrial cooling water and to take more restrictive steps concerning its disposal. At the present time one of the common approaches for controlling calcium carbonate scale formation is to use an organic phosphorous scale inhibitor conjointly with other additives to avoid corrosion or bacterial fouling. But high levels of phosphates are becoming increasingly restricted in terms of release to the environment. The same is true for some metallic additives such as for example zinc.

Environmentally acceptable chemical treatment regimes were developed using low or no phosphorous-containing inhibitors. Recently multifunctional biodegradable polyamino-acids such as polyaspartates have been proposed as alternate inhibitors for both scale deposit and metallic corrosion and also as dispersants 1-3. In addition to centralizing in one product all these functions thus theoretically driving to significant savings in chemical costs and handling and also in potential incompatibility problems, these polymers can be synthesized by various routes 4 leading to a promising optimization of their performances.

In the present paper the efficiency of polyaspartates as corrosion and calcium carbonate scale inhibitors and also as dispersive agents has been evaluated and compared to that of other well known inhibitors such as some phosphonates or polyacrylates. According to their properties the question arises if polyaspartates can be considered only as biodegradable alternates to polyacrylates 5 or if already they can compete with actual complete chemical treatments as noteworthy multifunctional green inhibitors 3'6. The aim of this evaluation is therefore also to look after some answers to these questions.

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