Since a few years corrosion phenomena (on the juice side) have appeared suddenly in the evaporators of some belgian sugar factories. In order to facilitate the investigation on that subject, the authors have applied iron analysis by atomic absorption as a means for quick detection of the corrosion.
It is showni that one should not limit the comparative analyses to only the thin and thick juice. In some cases indeed, iron was dissolved in the first effects of the evaporator (and mainly where the juice reached 20 to 25 Brix), but it redeposed in the further parts of the evaporation. It means that, for getting a better picture of the corrosion phenomena, one should also compare the iron content of the thin juice with a juice of about 30 Brix.
The analytical method was worked out during the 1969 campaign and was then applied in 1970 to daily samples of 19 belgian sugar factories. Among them five showed a corrosion in the evaporation. One factory was followed in detail. The corrosion could be stopped by adding caustic soda for increasing the pH value of the juice. An interruption of that soda addition made however the corrosion reappear. It indicated that, even at high pH values, the juice was not depositing a protective layer on the evaporator tubes.
Cathodic protection was tried out in one factory, the building of a protective magnetite layer (before campaign) in another factory. Both methods showed to be unsuccessful as to their results.
It is very difficult to know the exact reason for these corrosion phenomena. Among the information described in the literature, a progressive change of the nature of the non-sugars seems the most acceptable. Further trials on that subject are planned for the next campaign.
Proceedings: CITS 1971
pdf download: CITS1971-555-574.pdf