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One of the weak parts of these Udor Zeta Chlorine Pumps are the stainless steel valve springs! 

Back when we used pumps like the Udor Zeta series, we had valve springs custom made for us out of pure hastelloy!

LOL, we never got the chance to have the stainless steel valve springs in the Udor Zeta pumps made out of Hastelloy, because the pumps failed so much in other ways.

S H Effects on 304L Stainless Steel 

Cleaning regimens in food processing plants subject wall and ceiling coverings, 

equipment and other materials to very harsh conditions that are not normally present in 

other types of commercial and industrial environments. The surfaces of insulated metal 

panels are particularly vulnerable because high-pressure spray, hot water and various 

chemicals impinge directly on the panel facings and paint coatings multiple times each 

day. All paint coatings and facing materials will perform better or worse under these 

harsh procedures, and each material has some disadvantages to consider. 

 Exposure of stainless steel to chemicals containing chlorides will cause the 

chromium component on the surface to dissolve. This permits the free iron in the 

stainless steel to react with oxygen to form rust. Ceiling panels tend to be more 

susceptible to this phenomenon than wall panels. 

As water from the wash-down process begins to evaporate, the humidity level in the 

room rises and condensation containing chlorides starts to form on the face of the panels. 

This evaporation process concentrates the chlorides, which remain on the panel faces 

after all the condensation has completely evaporated. 

Excerpts from an article by John Tverberg explain more clearly the mechanics of this 

phenomenon. 

“What is stainless steel? Stainless steel is not a single alloy, but a large family of 

alloys with different properties for each member. There are hundreds of grades 

and sub grades in the stainless steel family, each designed for a special 

application. Chromium is the magic element that transforms iron into stainless 

steel. Stainless steel must contain at least 10.5 percent chromium to provide 

adequate resistance to rusting, and the more chromium the alloy contains, the 

better the corrosion resistance becomes. But there is an upper limit to the amount 

of chromium the iron can hold, so additional alloying elements are necessary to 

develop corrosion resistance to specific media.” (304 Stainless is 16% chromium) 

“We must remember that stainless steel is an alloy of iron. According to its 

definition, stainless steel must contain a minimum of 50 percent iron. If it 

contains less iron, then the alloy system is named for the next major element. For example, if the iron is replaced with nickel, so that the iron is less than 50 percent, 

it is called a nickel alloy.” 

“Chromium imparts a special property to the iron that makes it corrosion resistant. 

When the chromium is in excess of 10.5 percent, the corrosion barrier changes 

from an active film to a passive film. Whereas the active film continues to grow 

over time in the corroding solution until the base metal is consumed, the passive 

film forms and stops growing. This passive layer is extremely thin, in the order of 

10 to 100 atoms thick. It is composed mainly of chromium oxide, which prevents 

further diffusion of oxygen into the base metal. But, chromium also is stainless 

steel’s Achilles heel. The chloride ion is stainless steel’s nemesis. The chloride 

ion combines with chromium in the passive layer, forming soluble chromium 

chloride. As the chromium dissolves, free iron is exposed on the surface and 

reacts with the environment forming rust.” 

Special care and cleaning recommendations for stainless steel are available from The 

Specialty Steel Industry of North America on their web site, www.ssina.com in a 

handbook titled “The Care and Cleaning of Stainless Steel”. It provides specific 

information for properly maintaining various types of stainless steel. 

Thoroughly rinsing all of the surfaces in a wash-down area with fresh water, including 

the ceilings will minimize the potential for chlorides to damage the chromium oxide, 

passive layer. In addition, circulating air across the ceiling surface can help prevent 

condensation from forming in the first place. 

Metl-Span, LLC 

Lewisville, TX