Zahner® Resources

Zahner®  Resources > Contaminants

Common Contaminants

There are four major common contaminants, labeled Type A - Type D; some contaminants are more prevalent in certain areas, and certain metals are better at handling some contaminants than others. For instance, stainless steel, a metal known for its strength and resilience, will deteriorate under certain conditions where Aluminum would not, and vice versa.

Type A (mild adherence)

mild soot
evaporation patterns
airborne particles

Type A contaminants can be cleaned from the surface of nearly any metal using hot water and amild detergent.  Pressure washing will also aid the cleaning of the metal surface. (Note care in not driving water into the seams between metal panels).

Such cleaning processes can be performed on most lacquered and patinated metal surfaces
without harming the protective oxide layers.  It is recommended to clean metal surfaces this
way at least yearly.

Type B (mild adherence)

greases and oils
grease pencils
fingerprints
adhesives
hard water spots and scale

Type B contaminants are more adherent and require something that will dissolve and displace
the oils or organic polymers used as binders.  Xylene will work on metal surfaces without
harming them, as will window cleaners containing vinegar or citrus based, biodegradable
cleaners.  Note, if a lacquered coating is on the metal, solvents and strong cleaners can damage
or remove the lacquer.

There are a variety of cleaners available at local hardware stores that contain varieties of
solvents.  Some solvents work well on dissolving and displacing hydrocarbon based oils and
paints while others work better on acrylic polymer based adhesives.  Thoroughly rinse the
surface after cleaning.  You can follow up with a window cleaner to remove streaking.

Type C (strong adherence  partial etching)

dirt deposits from silicone joints
bird waste
concrete splatter
plaster
silicone
baked on substances
chlorides such as de-icing salts (before chemical attack or rusting)
paint and graffiti

Type C contaminants can be daunting.  Removal of these can remove the oxide layer and
lacquers if present.  Attempt the solution for the Type A contaminants first.  Direct pressure of
the washing nozzle to the proximity of the contaminant and see if this removes the particles.  If
the contaminant is new and has not yet developed molecular bonds with the metal surface it
should release.  At this point, various techniques for different metal finishes should be
considered.

Aluminum   Mild abrasive slurry can be considered.  Test an area of the surface first.
Scratching anodized surfaces can ruin them so exercise caution.  Lacquer thinners or paint
removers will not have a detrimental effect on the metal surface.

Copper and Copper Alloys  Any abrasive will remove a portion of the oxide or patina that is
present on the surface. This will have to be restored after cleaning.  Removal of paints and
graffiti using lacquer thinner or other paint remover should have little effect on the copper
oxide.  Sealants and the oils they exude will brighten the copper surface in the proximity of the
seal or where run off waters collect. Compounds emitted from sealants, even years after they
are applied, inhibit the natural oxide growth copper and copper alloys are known for.  The
sealant needs to be removed or sealed over with a paint coating if possible.  Otherwise, expect
continued brightening.

Stainless steels   Consider a copper knife or copper scraper to remove adherent particles.
Used correctly, the soft copper will not scratch the stainless steel surface. Chlorides are the
greatest concerns to stainless steels.  These should be removed at the earliest possible time to
prevent etching the surface.

Titanium   Titanium has an exceptional hardness and thus a copper knife can be used similar
to stainless steel.  The oxide can be scratched if other abrasives are used.  Very few solvents
will harm titanium.  Salts can be washed from the surface.
Zinc   Zinc is a soft metal and its oxide is also very soft.  Many substances will stain zinc
surfaces as they decay and interact.  Salts and bird waste should be removed before they have
the opportunity to decay.  Mild abrasives can be used.  It is suggested that test areas be tried.

Most solvents used to remove paint will not affect the zinc oxide.  The trouble is the porosity of
the zinc surface holds the paint, making it more difficult to remove.

Type D (chemical attack)

rust
oxides, sulfides and carbonates
heat tint / discoloration from heat oxidation
steel rust particles

Type D Contaminants are molecular interactions with the ambient.  The chemical and atomic
bonds made are not removable without the removal of some of the surface.  For stainless steels
that have been attacked by de-icing salts or other halogen salts, the rusting that results can be
cleaned with commercial rust removers.  Generally, they involve dilute phosphoric acid.  After
removal, thoroughly rinse the surface.  Heat tinting oxides on steel or stainless steels can
successfully be removed using phosphoric acid based cleaners.  Phosphoric acid based cleaners
will dissolve the oxide surface from copper alloys leaving them bright.

Zahner has proprietary solutions for cleaning a number of oxides, sulfides and carbonates from
metals.  Stains such as white staining of zinc or galvanized surfaces, dark red stains on lead or
terne surfaces can be removed.  Feel free to contact us to discuss your specific requirements.