ASTM B322-99(2020)e1

• Abstract:

  SIGNIFICANCE AND USE; 2.1 The performance and quality of electroplated articles depend upon the surface cleanliness and condition. Various metals are electroplated for decorative or engineering finishes. The common electroplates applied are usually copper, nickel, and chromium for decorative and functional uses. Electroplated articles are used in many industries such as the marine, automotive, plumbing fixtures, and appliance industries.; SCOPE; 1.1 This guide describes the procedure for cleaning metal surfaces to obtain good adhesion of electrodeposited metals. The degree of cleanliness required for metals to be electroplated is greater than for most other finishes. Methods of removal of heat-treat or mill scale are not included in these methods, because they are covered in practices referring to specific metals. It should also be understood that while these procedures are broadly applicable, particular substrates may require certain specific cleaning procedures. ; 1.2 Adequate cleaning requires a proper combination of cleaning procedures. The choice of these procedures must be based on a knowledge of the metals to be cleaned and of the soils to be removed. Because most experience and knowledge in cleaning have been obtained by suppliers of proprietary processes and formulations, these sources should be consulted before setting up a cleaning process. ; 1.3 A treatment to remove tarnish, light rust, fingerprints, or oxides is usually provided before immersion of the piece in the electroplating tank. This treatment activates the metal and is usually accomplished in acid baths which also serve to neutralize the residual alkaline film from alkaline cleaning. Alkaline chelated derusting and cleaning solutions, alone or with sodium cyanide, used as a soak or electrocleaner, are often preferred before electroplating on ferrous alloys. ; 1.4 Invariably several stages are necessary to provide adequate cleaning. These stages are discussed in three parts: ; Part I—Precleaning (use of a solvent, emulsion, or alkaline spray) to remove the bulk of the soil. ; Part II—Intermediate (alkaline) cleaning. ; Part III—Final electrocleaning, to remove trace solids and especially adherent impurities. ; Part IV—Trouble shooting. ; Often, depending largely on the amount and type of soil on the workpieces as received, one or more of these stages may be eliminated or modified. Usually, even with light soils, it is advisable to retain multistage cleaning, thereby increasing the life and efficiency of the cleaning solutions. ; 1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. (For more specific safety precautionary statements see Sections 11 and 16.) ; 1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

• Status: Published
• Publication Date: 31-Oct-2020
• ICS: 25.220.40 - Metallic coatings
• Technical Committee: B08 - Metallic and Inorganic Coatings
• Drafting Committee: B08.02 - Pre Treatment

Overview

ASTM B322-99(2020)e1 is the internationally recognized standard guide for cleaning metals prior to electroplating, developed by ASTM International. This guide outlines practical procedures to ensure that metal surfaces achieve the necessary cleanliness for successful electrodeposition, such as copper, nickel, and chromium plating. The quality and durability of electroplated finishes, both decorative and functional, are highly dependent on how thoroughly the substrate is prepared. Metal cleaning is especially important in industries like marine, automotive, appliance manufacturing, and plumbing, where reliability, appearance, and corrosion resistance are critical.

Key Topics

• Significance of Surface Preparation: Proper cleaning is crucial for achieving good adhesion and high-quality electroplated coatings. The cleanliness required exceeds that for other finishes to avoid defects like poor adhesion or inconsistent plating.
• General Cleaning Process: Cleaning procedures include precleaning (solvent or alkaline spray), intermediate (alkaline) cleaning, final electrocleaning, and troubleshooting. Each stage removes different kinds of soils and contaminants, from bulk residues to trace impurities.
• Types of Contaminants: Soils often encountered include buffing compounds, lubricants, fingerprints, oxides, rust, drawing or stamping compounds, and residues from handling or storage.
• Factors Influencing Procedure Selection: The choice of cleaning method depends on the metal type, fabrication process, kind of soils present, and subsequent handling. Certain metals, such as aluminum and zinc, require tailored processes to prevent damage like pitting or tarnishing.
• Importance of Multi-Stage Cleaning: Frequently, multiple cleaning stages are utilized, as each addresses specific groups of contaminants, enhancing the effectiveness and lifespan of cleaning solutions.
• Rinsing and Cleanliness Verification: Effective rinsing is vital to remove all cleaner residues. Common tests like the water-break test are used to evaluate surface cleanliness before plating.

Applications

ASTM B322 is highly valued in sectors where electroplated metal parts are essential. Typical applications include:

• Automotive Manufacturing: Ensuring that parts such as bolts, nuts, and external trim receive adherent and corrosion-resistant coatings.
• Marine Industry: Preparing surfaces for electroplating that resists harsh saltwater environments.
• Plumbing Fixtures: Guaranteeing that fixtures have decorative finishes that will not degrade in use.
• Appliance and Electronics Manufacturing: Achieving uniform and durable coatings for both appearance and electrical performance.
• General Metal Finishing: Any process where metals are electroplated for functional or decorative purposes benefits from following the cleaning standards in ASTM B322.

Related Standards

For organizations seeking to optimize metal cleaning and plating quality, several standards may be relevant alongside ASTM B322:

• ASTM B571: Standard Test Methods for Adhesion of Metallic Coatings
• ASTM B183: Standard Practice for Preparation of Low-Carbon Steel for Electroplating
• ASTM B280: Standard Specification for Seamless Copper Tube for Air Conditioning and Refrigeration Field Service
• ISO 9587: Metallic and other inorganic coatings - Pretreatments of iron or steel to reduce the risk of hydrogen embrittlement
• ISO 2080: Definitions related to electroplating and related processes

By following the guidelines in ASTM B322-99(2020)e1, manufacturers and finishers can achieve consistently high-quality electroplated metal products, improve process reliability, and meet the rigorous demands of international markets.

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
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Designation: B322 − 99 (Reapproved 2020) Endorsed by American
Electroplaters’ Society
Endorsed by National
Association of Metal Finishers
Standard Guide for
Cleaning Metals Prior to Electroplating
This standard is issued under the fixed designation B322; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
ε NOTE—Editorial corrections were made throughout in December 2020.
INTRODUCTION
This guide is intended to illustrate general principles of cleaning prior to electroplating. It is not
meant to apply to every specific application. In specific cases, cleaning practice may depart from the
general principles given in this guide.
1. Scope 1.4 Invariably several stages are necessary to provide ad-
equate cleaning. These stages are discussed in three parts:
1.1 This guide describes the procedure for cleaning metal
Part I—Precleaning (use of a solvent, emulsion, or alkaline
surfaces to obtain good adhesion of electrodeposited metals.
spray) to remove the bulk of the soil.
The degree of cleanliness required for metals to be electro-
Part II—Intermediate (alkaline) cleaning.
plated is greater than for most other finishes. Methods of
Part III—Final electrocleaning, to remove trace solids and
removal of heat-treat or mill scale are not included in these
especially adherent impurities.
methods, because they are covered in practices referring to
specific metals. It should also be understood that while these
Part IV—Trouble shooting.
procedures are broadly applicable, particular substrates may
Often, depending largely on the amount and type of soil on
require certain specific cleaning procedures.
the workpieces as received, one or more of these stages may be
eliminated or modified. Usually, even with light soils, it is
1.2 Adequate cleaning requires a proper combination of
advisable to retain multistage cleaning, thereby increasing the
cleaning procedures. The choice of these procedures must be
life and efficiency of the cleaning solutions.
based on a knowledge of the metals to be cleaned and of the
soils to be removed. Because most experience and knowledge
1.5 This standard does not purport to address all of the
in cleaning have been obtained by suppliers of proprietary
safety concerns, if any, associated with its use. It is the
processes and formulations, these sources should be consulted
responsibility of the user of this standard to establish appro-
before setting up a cleaning process.
priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
1.3 Atreatment to remove tarnish, light rust, fingerprints, or
(FormorespecificsafetyprecautionarystatementsseeSections
oxides is usually provided before immersion of the piece in the
11 and 16.)
electroplating tank. This treatment activates the metal and is
1.6 This international standard was developed in accor-
usually accomplished in acid baths which also serve to
dance with internationally recognized principles on standard-
neutralize the residual alkaline film from alkaline cleaning.
ization established in the Decision on Principles for the
Alkaline chelated derusting and cleaning solutions, alone or
Development of International Standards, Guides and Recom-
withsodiumcyanide,usedasasoakorelectrocleaner,areoften
mendations issued by the World Trade Organization Technical
preferred before electroplating on ferrous alloys.
Barriers to Trade (TBT) Committee.
2. Significance and Use
This guide is under the jurisdiction of ASTM Committee B08 on Metallic and
Inorganic Coatings and is the direct responsibility of Subcommittee B08.02 on Pre
2.1 The performance and quality of electroplated articles
Treatment.
depend upon the surface cleanliness and condition. Various
Current edition approved Nov. 1, 2020. Published December 2020. Originally
metals are electroplated for decorative or engineering finishes.
approvedin1958.Lastpreviouseditionapprovedin2014asB322 – 99(2014).DOI:
10.1520/B0322-99R20E01. The common electroplates applied are usually copper, nickel,
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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B322 − 99 (2020)
and chromium for decorative and functional uses. Electro- determining factor in cleaner selection. Aluminum requires
plated articles are used in many industries such as the marine, care to avoid overetching in alkaline cleaners; both aluminum
automotive, plumbing fixtures, and appliance industries. and zinc are sensitive to pitting attack, zinc and brass to
tarnishing. Zinc die castings have surfaces that require special
3. Nature of the Soil
care because of sensitivity to attack by cleaning solutions. If
possible, design of parts should avoid small indentations that
3.1 Some of the soils commonly encountered in electroplat-
tend to trap solid particles or buffing compositions. With die
ing are:
castings, care must be exercised to avoid cutting through the
3.1.1 Solid buffing compounds containing waxes, fatty
surface by excessive buffing. The subsurface is usually more
acids, and abrasives.
sensitive than the“ skin” of the casting. Some surface defects
3.1.2 Liquid buffing compounds.
may not show up until cleaning and electroplating cycles are
3.1.3 Drawing and stamping compounds including those
completed.
containing fillers (pigments).
3.1.4 Machining oils.
5. Cleaner
3.1.5 Rust-preventive slushing oils or greases.
5.1 It is essential that proper cleaners and operational
3.1.6 Electroplater’s stop-off residues.
conditions be selected. Attention should be given to proper
3.1.7 Fingerprints.
procurement since, even in the same category, not all cleaners
3.1.8 Dry dirt from storage or dry pickling smut formed
are equally effective. A cleaner may be very effective for one
during derusting by pickling.
group of soils, yet poor for other soils. This is true of
3.1.9 Rust or oxide scales, especially admixed with oil,
electrocleaners as well as soak or spray cleaners. Soil, type of
including heat-treat scales after oil quenching.
water, available time, rinsing facilities, type of metal, heating,
3.1.10 Phosphate coating with or without lubricant.
and agitation available, facilities for disposal of cleaner, and
3.1.11 Smut resulting from improper vapor degreasing of
type of personnel and equipment all influence the selection of
heavily buffed work.
cleaners. Obviously, economics must be considered but an
3.1.12 Smut resulting from annealing parts without pre-
initialorperpoundcostmustbebalancedagainstotherfactors.
cleaning between drawing operations.
3.1.13 Heat-treating salts, with or without quenching oils. 5.2 Cleaners do not work effectively indefinitely. The effec-
tive life of a cleaning bath must be estimated and baths
3.2 Consideration should be given to control of the soil. For
discarded when exhausted. Bath life is influenced by some of
example, efforts should be made to avoid overbuffing, leaving
the factors mentioned above as well as by the volume of work
excessivecompoundonthework,oragingofthecompoundon
processed. The concentration of the cleaner should be con-
the part before cleaning. Substitution of liquid for solid buffing
trolled by analysis at regular intervals.
compound, if work permits, often gives easier cleaning, if
properly applied, but may require use of a different type of
6. Rinses
cleaner. Drawing compounds with polymerizing oils or white
6.1 Water hardness, acidity or alkalinity, and impurities are
lead pigment are to be avoided because of difficulty in
important factors in rinsing (1). Distilled or demineralized
cleaning. Additives for lubricating and sulfurized cutting oils
water is preferred where impurities in rinse water must be kept
are chosen for their ability to adhere tenaciously and are
to a minimum. Boiler condensate may also be used advanta-
difficult to remove. Prolonged storage or drying of emulsion
geously. If the plant conditions water for acidity or alkalinity
drawing compounds after metal working should be avoided so
care must be taken to be sure the solids content is not too high
that slimy water-in-oil emulsions do not form. In-process
(Note 1). Impurities derived from processing cannot be ig-
cleaning or even a hot-water flush before storage is helpful.
nored; that is, rinse waters must be changed frequently or
Emulsion machining lubricants (soluble oils) should be used in
overflowed continuously (Note 2). Counterflowing rinses are a
place of sulfurized cutting oils if operations permit. Lower-
distinct advantage in obtaining good rinsing with economical
viscosity machining and rust-preventive oils are more easily
use of water.
removed. Stop-off materials, when used, should be applied
carefully in order to avoid contaminating significant surfaces. NOTE 1—Boiler waters which contain cationic corrosion inhibitors may
be quite detrimental to the plating process.
The use of clean gloves should be mandatory after buffing or
NOTE 2—Floating oil on water can cause poor adhesion.
polishing to avoid fingerprints on the work.Airborne contami-
nants can be avoided by using covers over stored work. It is
7. Equipment
desirable to perform a cleaning operation as soon as possible
7.1 It is important to provide enough room in the plant for
after metal forming, polishing, or buffing to reduce the de-
an adequate cleaning cycle. A discussion of equipment is
mands on subsequent cleaning operations, because many soils
beyond the scope of this practice (2, 3).
are more easily removed when fresh.
8. Criteria of Cleanliness
4. Metal
8.1 This subject has been treated exhaustively in the litera-
4.1 The properties of the metal and the method of fabrica-
ture (4). The atomizer test is the most sensitive one, but the
tion and handling of parts play a role in cleaning. The softness
and surface finish of the metal are factors in selecting handling
The boldface numbers in parentheses refer to the reports and papers appearing
methods.Thechemicalactivityofthemetalisanimportantand in the list of references at the end of this practice.
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B322 − 99 (2020)
water-break test is most commonly used. This involves visual because it cleans by solvent action instead of chemical action;
observation after a final rinse in clear, cool water.Acontinuous there is no danger of over-cleaning or under-cleaning because
sheet of water on the part usually indicates a clean surface. of any difference in chemical activity of the metals present.
(Certain precious-metal surfaces, such as gold, may exhibit Because of the rapid penetrating action of the solvent and
water break, even though clean.) Some experience is necessary solvent vapor, this method is effective in cleaning parts
to judge the appearance of a break in the film of water. A containing recesses, blind holes, perforations, crevices, and
specific drainage time, about 30 s, should be used before welded seams. Where the soils are present on surfaces that are
observation. not readily accessible, the process is sometimes supplemented
by ultrasonic cleaning in the solvent rinse chamber.
8.2 A dip in clean, dilute acid and reexamination are
10.3.2 Vapor degreasing is effective on solvent-soluble soils
desirable to avoid false water-film continuity due to adsorbed
and chemically active lubricants. Insoluble soils (buffing grits,
soaps. Other methods, including electroplating and testing of
metal chips and dust, etc.) are flushed away as the soluble soils
the electroplate, should be used occasionally to confirm visual
(greases and oils) dissolve in the solvent. It is not effective on
examination. (One procedure involves scrubbing with pumice
metallic salts, scale, carbon deposits, many inorganic soldering
and then comparing the surface produced by this method with
or welding fluxes, and fingerprints unaccompanied by oil or
that produced under production conditions.)
grease. This process is frequently competitive in cost with wet
PART I—PRECLEANING cleaning methods. Its lower equipment, floor space, and heat
requirements offset the higher cost of solvent.
9. Purpose
10.3.3 For some applications (steel stampings, buffed zinc-
9.1 Precleaning is designed to remove a large excess of soil, base die castings, etc.), the degreased work can go directly to
mild electrolytic cleaning and subsequent electroplating with-
especially deposits of buffing compound or grease. It is also
useful in reducing the viscosity of waxes and heavy oils, to out the need for an intermediate alkaline cleaning step.
enablelatercleaning stages to be more effective, or tosurround
10.4 Emulsion Cleaners—Oils and high-boiling hydrocar-
fingerprints and dry dust with an oily matrix to facilitate
bonssuchaskerosenehavetheabilitytodissolvemostgreases,
removal by alkaline cleaners.
particularly at high temperatures. The addition of emulsifiers,
soaps, and wetting agents enhances the penetrating power of
10. Types
the organic solvent and permits removal of the latter and
10.1 Cold solvent, vapor degreasing, emulsifiable solvent,
associated soil by power flushing. Further, intimate contact of
solvent emulsion spray, invert-type emulsion cleaners, or hot
the metal surface with the aqueous phase permits removal of
alkaline spray with or without solvent emulsion can be used
materials not soluble in the hydrocarbon phase.
(5).
10.4.1 The principle of emulsion cleaning can be applied in
a variety of ways including the use of straight emulsifiable
10.2 Cold Solvent (6)—Mineral spirits; trichloroethylene;
perchloroethylene; 1,1,1,-trichloroethane (methylchloroform); solvents, unstable emulsions (diphase cleaners), invert-type
emulsion cleaners, and stable emulsions. Additions of rust
methylene chloride; or trichlorotrifluoroethane can be used for
coldcleaning.Combiningthesewithhandbrushingisexcellent inhibitors or of alkali cleaners can be made to the water phase.
Since agitation is important to good cleaning, the power-spray
but does not lend itself to production conditions. On the other
hand, simple dipping in solvent is frequently ineffective. The cleaners find wide applications.
10.4.2 Emulsion cleaners are used at temperatures up to
chlorinated solvents are very effective for many soils, but not
as effective in removing soap-based or other solvent-insoluble 82 °C. The higher temperatures remove soils more quickly and
effectively, but caution must be used with cleaners containing
soils. Before electroplating, cold cleaning with solvents must
be followed by additional cleaning such as alkaline cleaning to organics of low flash point. Some cleaners containing chlori-
remove slight oily residues. nated solvents are used above the flash point of some of the
components since the chlorinated portion will volatilize to
10.3 Vapor Degreasing (7)—Trichloroethylene and, to a
extinguish flashes.
lesser extent, perchloroethylene, trichlorotrifluoroethane, and
methylene chloride are used for vapor degreasing. In vapor 10.5 Biological Cleaners (8)—Highly emulsifying soak
degreasing, the work is usually sprayed with clean solvent or cleaners are combined with living microorganisms to permit
given a thorough immersion in boiling or warm solvent for the removed oils, greases, and other complex organic com-
mechanical removal of tenacious soil or solids. This is fol- pounds to undergo a natural process known as bioremediation.
Living microbes break down organic compounds, such as oil
lowed by immersion in cold solvent to cool the parts. Then
follows exposure to condensation of hot, clean solvent vapors and grease into carbon dioxide and water and the cleaners, if
properly maintained, may run for years without changing the
on the work. This final step also removes any last traces of oil
and grease and dries the part. For removal of caked-on oils and bath at all. Since the cleaning fluid is kept free from
contaminants, the such systems allow more effective cleaning
compounds, a predip in cool solvent can be used to wet and
loosen the soil before the degreasing operation. for a greater length of time.
10.3.1 Vapor degreasing can be used to clean all types of 10.5.1 In order to maintain a healthy biosystem, operating
metal, including steel, steel alloys, light metal alloys, special conditions are critical. Typically, optimum pH range for these
bronze, nonferrous metals, nickel, and titanium. This method types of cleaning systems is 8.5 to 9.5. Too high a pH will
simplifies the cleaning of parts containing several metals result in lowering of the bacteria action, and oil will be
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B322 − 99 (2020)
built-up. Too low a pH will render the bacteria too active cleaners can also require water conditioning in hard-water
resulting in consumption of the wetter and other organics areas to avoid precipitation of hard-water soaps. Good house-
necessary for proper cleaning. Temperature also is a critical keeping is desirable to avoid bacterial contamination of emul-
operating parameter. Optimum metabolism of oil and grease is sion cleaners. Bacteriostats can be included in the formulations
achieved around 40 to 50 °C. of cleaners to prevent the unpleasant odors that result from
bacterial action.
10.5.2 Air agitation is critical to maintaining an oxygenated
environment to maintain sufficient biological activity and only
11.5 As indicated in 14.7.8, disposal of emulsion cleaners
aerobic bacteria. Without air during operation, anerobic bacte-
can present problems.
ria are produced and the cleaner will take on a noticeable,
PART II—INTERMEDIATE (ALKALINE) CLEANING
unpleasant odor. Air sparging also improves overall cleaning
efficiency by promoting transfer of oil and grease particles
12. Purpose
from part surface into the cleaning solution. In order for
bioremediation to proceed, particles must be detached from the
12.1 Intermediate alkaline cleaning removes solvent resi-
part surface.
dues and residual soil which has been softened or conditioned
by precleaning. Spray or soak alkaline cleaning also can be
11. Precautions
used as a precleaning stage followed by additional alkaline
cleaning,ifthesoilandmetallendthemselvestothistreatment.
11.1 The use of solvents and emulsions of diphase cleaners
This is not so for metals that are sensitive to alkaline cleaning,
requires special attention to safety hazards. Petroleum and
such as zinc, because the time in the alkaline cleaner should be
aromatic solvents of low flash point, for example less the
minimal. Some electroplaters use the term precleaning for
55 °C, must be used with caution. Underwriters Laboratories-
alkaline cleaning before electrocleaning, especially when sol-
approved containers and adequate ventilation should be pro-
vent cleaning is carried out at a different part of the plant.
vided to avoid the accumulation of fumes in explosive concen-
trations. Diluted emulsion cleaners usually have flash points
12.2 Although industrial practice is limited, vapor degreas-
above 70 °C and emulsifiable solvents of high flash point are
ing alone is sometimes used before electrocleaning. Most oils
now available.
and greases and some buffing and drawing compounds are
effectively removed and contamination of the electrocleaning
11.2 Trichloroethylene and perchloroethylene are nonflam-
bath is lessened. The specific applications will not be given in
mableundertheconditionsofthevapordegreasingprocessand
detail here (5, 6, 7). Manufacturers of degreasing solvent or
are among the least toxic of the chlorinated hydrocarbons; up
equipment should be consulted for details.
to 100 ppm of either is tolerable in the working atmosphere for
a normal 8-h working day. Trichlorotrifluroethane (1000 ppm
13. Types
tolerable limit) is also used. With proper equipment design and
13.1 Soakalkalinecleaningiscarriedoutat30to120g/Lof
operation, solvent vapors in the working area are easily
alkaline cleaner at temperatures of 82 °C to boiling, for periods
maintained well below recommended safe limits. Degreaser
of 3 to 15 min. If used ultrasonically, temperatures may be
tanks should preferably be cleaned and maintained from
70 °C to boiling. The cleaners usually contain surface-active,
outsidethetank.Entryintoatankshouldbemadeonlyafterall
soap-like materials which foam if agitated vigorously.
solvent and vapors have been removed and then only with an
observer on the outside. Proper ventilation cannot be over-
13.2 Spray alkaline cleaning is usually carried out at 4.0 to
stressed because workmen will often discard a recommended
15 g/Lat temperatures of 50 to 82 °C for 1 to 3 min with spray
gas mask. For cold-solvent operations, adequate ventilation
pressures of 69 to 345 kPa (10 to 50 psi). Foaming may be a
must be provided in the work area.
problem, unless the cleaner is properly designed.
13.2.1 Foam is also a major problem because of accumula-
11.3 Becausesoilsaccumulateinsolvents,thesolventsmust
tion of soaps in the cleaner from the action of the alkali on
be discarded or purified by distillation. In vapor degreasing
someorganicsoilsanddrag-inofwettersfromprecleaners.For
equipment, the solvent is recovered by distillation and the soil
this reason, it frequently is desirable to use low concentrations
discarded. The use of automatic auxiliary stills in conjunction
of cleaner, for example, 4.0 g/L, and to discard the solution
with the degreaser allows continuous cleaning operation and
often, even though cleaning is adequate. For the same reason,
solvent recovery.
it is sometimes necessary to operate at lower pressures even
11.4 Emulsifiable solvents must be discarded occasionally,
though higher pressures give better cleaning.
although frequently most of the soil is flushed off in the rinse.
13.3 Barrel alkaline cleaning is usually carried out at 7.5 to
Emulsion cleaners represent a particular problem of bath
45 g/L. Temperatures are usually lower than for soak cleaning
contamination because of the lack of adequate analytical
becauseofmechanicalfactors.Althoughagitationisbetterthan
controls to determine bath life. Because emulsion cleaners
in some cleaning, control is frequently not as good.
yieldawater-sheddingsurface,theeffectonwater-breakdueto
accumulated oils is difficult to differentiate from that due to the
14. Factors Influencing Good Alkaline Cleaning
solvent. Because of the low cost of diluted emulsion cleaners,
it is economical to discard these baths at frequent intervals. 14.1 Concentration—The optimum concentration of the
Soap-base emulsion cleaners can cause difficulties where cleaning solution should be determined by actual tests because
acidic soils are introduced; here mixed alkalies and emulsion many factors are involved.
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B322 − 99 (2020)
14.2 Temperature—Best results are obtained near the boil- of a free-rinsing cleaner may require some sacrifice in cleaning
ing point if other conditions permit. The high temperature properties. Rinse tanks should have adequate overflow rate,
reduces the viscosity of the soil. A rolling boil provides skimming troughs of good design, and proper positioning of
agitation. In some cases, cleaner formulation may be such as to the intake water line.
make lower temperatures optimal.
14.6.1 Agitationofworkintherinsetankisdesirable.Water
must also flow through hot rinses, although a reduced rate is
14.3 Time—Alkaline cleaners, operating by the mechanism
often desired for economy. Spray rinsing is very effective,
of lifting the oil film, require a reasonable time to permit the
especially if coupled with soak rinsing by having a spray of
surface-active materials to act on the surface. This time is
clean water hit the work as it exits from the rinse tank. Drying
shortened if agitation is vigorous, temperatures high, and
of the cleaner on the work before rinsing should be avoided by
concentration high. Age of solution and contamination retard
having fog nozzles after cleaning tanks, if necessary, or by
cleaning.
decreasing transfer time or operating temperatures. With some
14.4 Agitation:
cleaners, adequate rinsing is difficult to obtain after the cleaner
14.4.1 Spray Cleaning (2)—As in emulsion cleaning, much
has dried on the work.
of the effectiveness of spray cleaners in removal of solids is
14.7 Selection of the Cleaner—Important factors to be
due to the mechanical action of the solution sprayed on the
considered are as follows:
surface. Hence, every effort should be made to obtain efficient
14.7.1 Soil (see 3.1 and 3.2)—If the soil is rich in soaps, the
impingement at high pressure without pushing the work out of
cleaner should be lean in this respect and should have built-in
the spray area (or off the racks). Foaming after soap accumu-
high soap tolerance. Because of the specific action of the
lation also limits spray pressure. The action of spray alkaline
individual cleaners on certain soils, this is a prime factor in
cleaners depends on detergency as well as mechanical action;
cleaner selection.
the proper materials and conditions should be used. Spray
14.7.2 Metal (see 4.1)—Special cleaners are
...