Waukesha 200 series Operation And Maintenance Manual - Care of Stainless Steel
Care of Stainless Steel
Waukesha Cherry-Burrell
Page 6
95-03074
Issued: January 2003
Revised: June 2005
Care of Stainless Steel
Stainless Steel Corrosion
Corrosion resistance is greatest when a layer of oxide film is formed on the surface of stainless steel. If film is disturbed or
destroyed, stainless steel becomes much less resistant to corrosion and may rust, pit or crack.
Corrosion pitting, rusting and stress cracks may occur due to chemical attack. Use only cleaning chemicals specified by a
reputable chemical manufacturer for use with 300 series stainless steel. Do not use excessive concentrations, temperatures
or exposure times. Avoid contact with highly corrosive acids such as hydrofluoric, hydrochloric or sulfuric. Also avoid
prolonged contact with chloride-containing chemicals, especially in presence of acid. If chlorine-based sanitizers are used,
such as sodium hypochlorite (bleach), do not exceed concentrations of 150 ppm available chlorine, do not exceed contact
time of 20 minutes, and do not exceed temperatures of 104°F (40°C).
Corrosion discoloration, deposits or pitting may occur under product deposits or under gaskets. Keep surfaces clean,
including those under gaskets or in grooves or tight corners. Clean immediately after use. Do not allow equipment to set
idle, exposed to air with accumulated foreign material on the surface.
Corrosion pitting may occur when stray electrical currents come in contact with moist stainless steel. Ensure all electrical
devices connected to the equipment are correctly grounded.
Alloy 88
Waukesha Alloy 88 is the standard rotor material for Universal I, Universal II, Universal Lobe, Universal 420/520 and
5000 Series Rotary PD pumps. This alloy was developed specifically for corrosion resistance and close operating
clearance requirements of high performance rotary positive displacement pumps. Alloy 88 is a nickel based, corrosion-
resistant, non-galling or seizing material. The ASTM designation is A494 Grade CY5SnBiM (UNS N26055), and the
material is listed in the 3-A Sanitary Standards as acceptable for product contact surfaces.
The above properties make Alloy 88 the ideal material for Waukesha stainless steel PD pumps. The non-galling rotors
permit close operating clearances in the liquid end. This provides low slip and minimum shear damage. The rotors will not
gall or seize if they come in contact with the body or cover during operation.
The corrosion resistance of Alloy 88 is approximately equal to AISI 300 Series Stainless Steel. However, Alloy 88 has
limited resistance to certain aggressive chemicals that may be commonly used in contact with AISI 300 Series Stainless
Steel.
Do not use Alloy 88 in contact with nitric acid. Nitric acid is commonly used to passivate new installations of stainless
steel equipment. Do not allow nitric acid based passivation chemicals to contact Alloy 88 rotors. Remove the rotors
during passivation and use a separate pump to circulate the passivation chemicals. Also, if nitric acid-based CIP cleaning
chemicals are used, remove the rotors prior to CIP cleaning and clean them separately by hand in a mild detergent.
If you have questions regarding other aggressive chemicals, please contact Waukesha Cherry-Burrell Application
Engineering for assistance.
Elastomer Seal Replacement Following Passivation
Passivation chemicals can damage product contact areas of WCB equipment. Elastomers (rubber components) are most
likely to be affected. Always inspect all elastomer seals after passivation is completed. Replace any seals showing signs of
chemical attack. Indications may include swelling, cracks, loss of elasticity or any other noticeable changes when
compared with new components.