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OPERATING INSTRUCTIONS
62.9693.01 Page 10
8. TREATMENT OF COMMERCIAL KITCHEN
APPLIANCES
Commercial kitchen appliances are executed in corrosion
resistant chrome nickel steels, material numbers 1.4301 and
1.4404.
The corrosion resistance of these steels is based on a passive
layer formed on the surface with access to atmospheric oxy-
gen. Accelerated formation or reformation of the passivity
occurs by treating surfaces with running water containing oxy-
gen. Aggressive media with a reducing effect (oxygen con-
suming) such as substances containing hydrochloric acid,
chlorides and seasoning concentrates, mustard, vinegar
essence, seasoning or spice tablets, salt solutions, etc.,
depending on concentration and temperature, can result in
chemical damage or the destruction of the passive layer. Dam-
age can also result from foreign rust (iron particles) due to the
formation of galvanic elements and lack of oxygen (no air
access or low oxygen water).
Therefore the following principles should be observed when
working with high grade steel equipment:
1. Surfaces of equipment of corrosion resistant steel are
always to be kept clean and exposed to the air. Remove cov-
ers from utensils when not in use to provide free air access.
Regularly remove limescale, grease, starch and egg white
deposits by cleaning. Corrosion can occur under these layers
due to the absence of air exposure. Limescale can be
removed with 10% acetic acid, 10% phosphoric acid or with
suitable limescale removers available on the market.
2. Corrosion resistant steel objects must not be kept in long-
term contact with acids, spices and seasonings, salt, etc. Also
promoters of corrosion are acid vapours as produced during
floor cleaning. Contact surfaces are to be rinsed off with fresh
water. This applies after use, especially after cooking pota-
toes, noodles, rice etc. in salt water. Dried-on cooking water
residues form high concentration salt solutions which can
cause point corrosion. So, immediately after use, rinse cooking
utensils in fresh water or keep filled with cold water to cool
them. It is not advisable to use one utensil exclusively for cook-
ing e.g. potatoes in salt water. For stainless steel it is beneficial
to use utensils for different produce, e.g. for soups containing
fat or acid-containing vegetables (such as sauerkraut, for
example).
3. Stainless steel surfaces should, where possible, be pro-
tected from mechanical damage, especially from other metals.
Corrosion can occur if stainless steel comes into contact with
iron (steel wool, chips from pipes, water containing iron). New
corrosion locations can be removed with a mild abrasive or
fine emery cloth. Heavier corrosion can be washed off with a
warm 2-5% solution of oxalic acid. Treatment with 10% nitric
acid is necessary if this proves ineffectual. Due to the associ-
ated hazards, this type of cleaning is only to be carried out by
suitably trained staff in compliance with the valid regulations.
4. No bleaching or chlorine-containing cleaning agents are to
be used for cleaning. Utensils are to be thoroughly rinsed with
water and dried after cleaning. The surfaces of appliances are
of corrosion resistant chrome nickel steel. They are to be
washed down with hot soapy water with the addition of a
standard grease solvent. Avoid cleaning with steel brushes,
steel wool, copper scouring pads or cloths, products contain-
ing sand, etc. as such media destroy the surfaces and create
the conditions for corrosion formation. Spraying appliances or
parts of appliances with a water jet or high pressure cleaning
equipment is harmful and can cause malfunction. This is there-
fore prohibited.
Note:
The type and concentration of solvents used for cleaning the
surfaces must comply with the code of the Federal Regulations
21 CFR Part 178.1010.