Corrosion is also the most complex of all water-related issues simply because there are so many contributing factors. Due to the complexity of this topic, we will offer a series of postings to take a more detailed look at several water-related issues. The following is an overview.
Potential causes of corrosion in a Combi oven can be and are not limited to the following:
An unusual example that we have seen in various locations and with different brands of ovens is where two ovens are sitting side-by-side of the same make and model. One has been in service for less than three years and the other for twice as long. The older oven shows no signs of corrosion and the three year old oven looks like it is ready for the scrap yard with significant corrosion. The ovens had the same water supply, same operators, and were exposed to the same cleaners. Some in-depth investigation revealed that the three year old oven was operated at low temp (straight) steam 100% of the time; and the older oven in combo and in convection with no steam alternatively throughout the day, allowing the oven to dry out.
It is not uncommon for operators to see rust starting in corners or sliding racks and mistakenly use an acidic cleaner to try and remove it. This is comparable to throwing gasoline on a fire to try and put it out. Acid cleaners and de-scalers will accelerate the corrosion process increasing the amount of rusting. We also have seen operators use wire brushes to clean off deposits of food, scale or rust. Again, this only adds to the problem by scratching the surface of the stainless steel and leaving behind microscopic particles of iron in the scratches. These iron deposits act as a catalyst for new corrosion.
Major contributors to corrosion in ovens are chlorides and sulfates in tap water. Chlorides are naturally occurring in tap water at different levels throughout the country. Chlorides levels can be increased due to the concentration of surface waters and the influx of chloride containing effluents in the waste stream or runoff. Chlorides will concentrate in microscopic cracks, crevices and joints of your oven and will cause “Crevice Corrosion.” Most of the corrosion in Combi ovens is typically Crevice Corrosion due to the depletion of oxygen in the crevice, a shift to acid conditions in the crevice and a concentration of aggressive ion species (chlorides) in the crevice. It is important to know that a carbon or sediment filter or a Weak Acid Cation resin based filter will NOT reduce chlorides or sulfates in the tap water.
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