If your company works in the food & beverage, bio-medical or pharmaceutical industry, you will be familiar with the stainless steel sanitary tubes and fittings that your equipment depends on. Although stainless steel will never rust and comes with corrosion resistant annealed, pickled or polished finishes, the crevices between the ends of pipes and fittings are areas for concern. Here we will look at how corrosion occurs and how you can avoid or minimize this.
What Is Crevice Corrosion?
In this article we are looking at the crevices between stainless steel pipes and tubing and other pieces of metals including valves, fittings or caps. These narrow gaps where the two pieces join are the first and most common place for corrosive attacks to begin. It is essential that stainless steel is regularly cleaned and that all moisture is absorbed. This isn’t always possible in the crevices, though, but with a little understanding, crevice corrosion can either be avoided or minimized.
Your Pipe And Tubing May Have More Crevices Than You Think
Crevices can include the space under a washer or bolt head, the space around a valve, the gap between plates bolted together or between components welded together. Many people don’t consider the spaces under a sticky label or a metal name plate or the space between a gasket and the metal in a flange. All of these areas are potential points of crevice corrosion. Water and other contaminants get underneath and into these areas where they cannot be easily dried or wiped away. Over time, this means that the likelihood of corrosion is higher.
How The Environment Affects Crevice Corrosion
The crevices in your stainless steel pipes and tubes are more likely to be attacked with the liquid outside them is aggressive. This explains why crevices in a fresh water tanks are less affected than the cervices on stainless steel steps in a salt-water swimming pool.
Cleaning Methods Affect Crevice Corrosion
Crevices corrode more severely if the liquid they come into contact with is highly oxidizing. This is a good reason why bleach should never be used to clean stainless steel pipes and tubes. The best cleaning solution is water with 1 per cent ammonia solution. Bleach is too difficult to be used in the correct quantities and it is very hard to remove completely when cleaning has been completed. Bleach is very oxidizing and will cause crevices around your stainless steel pipes and tubes to be corroded more quickly.
Manufacturing Quality Helps Minimizing The Risk Of Crevice Corrosion
The quality of the pipe and tube design and fabrication will help to minimize crevice corrosion. Full penetration butt welds are best for joints while seal lap joints help avoid gaps between pipes and fittings where corrosion might occur. This is the best reason to source your stainless steel pipes and tubing from a reputable manufacturer who insists on quality manufacturing techniques. Although it may cost more upfront you stand to reduce the longer-term maintenance costs associated with corrosion.