PROCESSES FOR PLATlh,

Acid dip/rinse Co pper/ri n se Nickel/rinse An od ic t reat/ri nse C h ro m e/ri n s e C h ro mate/r i n s e

X X

X X X

i3N ZINC DIE CASTINGS

' , -

~

~

~

~~

~

~

X X

X

X PROCESSES FOR PLATING ON BRASS

I-

Alkaline cleankinse Acid d i d r i n s e Copper strikehinse Acid diphinse Co ppe r/r i n se NickeVrinse C h ro m e h i nse

I

12

Decorative Chrome Decorative Chrome Protective Chrome X X X

X X X

X X

X X

X X X

X X

X X X X X X

I

Standard Chemical and Electrochemical Production Process

Workpiece base material

1

, n

PROCESS BATH

,--(to

floor and to rinse system)

Workpiece to additional p r o d u c e n steps

RINSE SYSTEM

7

Prbduction chemicals

I

Spent baths (to treatment or disposal)

I

Fresh water

Wastewater (to treatment or discharge)

Electroplating industry is a subset of the metal finishing industry. application of maetallic coatings on surfaces by electrodeposition Includes both independent (job) platers and captive operations associated with product fabrication and assembly.

imately Z i % m p a n i e s involved in metal finishing; approximately upply only plating services. oximately&5%of the plating operations are in IL, MI and OH. Another are PA, CT, RI, NY and NJ. /boo P,I;{dQc.A Size of electroplating facilities ranges from 100 - 50,000 total gallons of process solution; 100 - 10,000 square feet of work processed daily. Parts being plated range in size from less than 1 sq in each to greater than 10 square feet each; in weight from less than 1 oz to more than 10 tons.

120,000 tons/yr of metal (mostly copper, nickel, zinc and tin) is plated onto parts. Coatings provide: corrosion protection wear or erosion resistance lubricity electrical conductivity heat and light reflectivity other special surface characteristics /

Plating allows the conservation of several million tons/yr of such critical metals as cobalt, chromium, nickel, silver and gold. Electroplated coatings usually range from 0.00025" to 0.0015"; heavier coatings (0.010'' to 0.015") may k used for engineering applications or ie rebuild wom parts. \;td f=oflut\,-fio t

4

Hundreds of plating solutions are commercially available, but only two or three basic types are used for most applications.

Basic operating sequence: 1) Cleaning (remove soils; may use solvents, aqueous cleaners, or both) 2) Rinse 3) Acid (remove oxidation) 4) Rinse 5) Electroplate 6) Rinse 7 ) Dry

In the electroplating solution, ,meta ons.-ixpeithef%Cid Takaline' o solution are reduced onto-@$ithode-surfaces (the work being plated). Metal ions in solution are replaced either through dissolution from anodes (bars hung from hooks or chunks in baskets) or by addition of metal salts. Barrels are used for small parts that tumble freely in in rotating barrels. Perforated plastic barrels range in size from 6 to 30 inches. Direct current loads of up to several hundred amperes are carried to the parts being plated through "danglers" suspended from a current-carrying bar. r:approximatel y re processed. Racks are composed of "spines" that are plastic-coated, with "tips" that have exposed copper for making contact with piece parts.

RSaCkS*alEUS

filters, rectifiers, etc.

filters, rectifiers, etc.

FIG. 1

A "common well" tank layout

/

FIG. 2

rinse chromate

Common well plus transfer tank layout

cadmium plate

chromate rinse

chromate

rinse chromate rinse

rinse

tin plate

rinse brass plate

rinse

rinse rinse

rinse

zinc plate

rinse

copper plate

rinse

nickel plate

cyanide dip

TRANSFER TO PLATING A

rinse

DRY

soak clean 1

STAGING AREA FOR WORK TO BE PLATED

rinse

hot water rinse loadlu nload

I

Q)

.% C

.

To r i n s e and d r y

Lo a d b a r r e 1 s

& 7

Soak c l e a n e r - - 1

Soak c l e a n e r - - 2

Rinse--3

b-

b

city

wastewater

1

E l e c t r o c l eaner--4

Electrocleaner--5

wastewater

I

Series rinse--7

Cyanide z i n c p l a t i n g b a t h - - ' 3

city water

L1-' A c i d bath--0

-

S e r i e s r i n s e - - 12

I

Acid bath--9

= water flow

I

E

= work flow

Cyanide zinc line existing rinsing arrangement

FIG. 4

Load b a r r e 1 s

To r i n s e and d r y

Chromate-- 19

Soak c l e a n e r - - 1

-

>

1"1 Chr

ate-- 18

e3

Soak c l e a n e r - - 2

S t r i p ank-- 17

1

3 gpm

Rinse--3

Oe3

D-

S e r i e r i n s e - - 16

~

b wastewater

II

--II

w a s t e w at e r

E l ec t r o c l eaner--4 I

I

E l ec t r o c 1 eaner--5

Drag-out--

Series rinse--6

Cyanide z i n c p l a t i n g bath--

+

c

14

3

wastewater

Series rinse--7

--

c

Drag-in-- 12

1 gpm

3 gpm cc

A c i d bath--8

Series rinse-- 1 1

wastewater ____)

-

Seriesrinse-- 1o

Acid bath--9

= w a t e r flow

= work flow

Cyanide zinc line new rinsing arrangement FIG. 5

1

TEXT FOR OVERHEADS Figures 1-5 Fig. 1 Common well tank layout This terminology applies to installations where all cleaning, acid treating and post-plating rinsing and drying are done in a "common well" or "kitchen sink" and the plating processing is done in surrounding process tanks. This layout works well when a wide variety of finishes must be plated but the volume of any one finish is not large. It also works well when plating times are long in relation to the time required for cleaning and rinsing. Two common applications are jewelry plating and hard chrome plating. Disadvantages are:

Capacity The cleaning and rinsing lines often prove to be undersized if the surrounding process tanks are to be kept full of work at all times. Uncontrolledfloorspills that complicate waste treatment by adding to its complexity and volume are more likely with this arrangement. Lack of automation This layout is nearly impossible to automate, making it difficult to take advantage of some waste dragout reduction techniques.

Fiy. 2 Common well plus transfer tank layout In this Iayout, the addition of a transfer tank allows for partial automation and for greater complexity and volume of plated finishes. This layout also can nearly eliniinated floor spills, if tanks are properly installed. This layout has many applications, but is most common where the substrate of the work varys only a little, e g , hardware, fixtures or hand tools. Disadvantages are: Capacity The capacity of the cleaninvg and rinsing line again deramine whether the process solutions can be kept at full capacity. Scheduling can sometimes be difficult, leaving some process tanks waiting for work while others are very busy. Flexibility To the extent that this layout is automated, production cycles are difficult to interrupt, a situation that can lead to higher volumes of waste, especially from rejects. Small runs can take an extremely long time to process, and may take an inordinate amount of attention by an operator.

2

TEXT FOR OVERHEADS Figures 1-5 Fig. 3 Big circle tank layout This layout is used for high-volume production of a limted number of parts and finishes. The loop may be a a circle, and oval, a rectangle or a back-and-forth loop as shown. All "full return" automatic plating machines use this layout. This layout is extremely and efficient and, because very little or very slowly, amenable to many types of waste reduction opportunities, as long adding equipment to the line is not required. Disadvantages are:

Flexibility This layout cannot be changed physically, and many times chemistry changes or changes the timing of process steps can be difficult to implement. This is because the work moves through the process on a continuous chain drive, and each step is directed to all others. Only where "skippers" can be used to adjust the process can major changes be made. Control Since the machine is large and interconnected, problems can go undetected for a long time. These may include: process solutions out of chemical control, causing rejects; leaks or spills; dropped parts causing contamination. Since any one part does not carry a very high value as a percentage of overall production, rejects are often tolerated at higher rates than would be acceptable with other layouts.

Fip. 4 Cyanide zinc barrel plating line Following is the operating sequence used on this plating line: 1) Barrels are loaded with parts at the loading area. Parts are assorted fasteners: bolts, washers,

nuts, screws and cotter pins. 2) Time in each process tank is as follows:

1--5 min 2--5 min 3--2 min 4--5 min

3

TEXT FOR OVERHEADS Figures 1-5 5--5 min 6--1 min 7--2.5 min 8--5 min 9--2 min 10--1 min 11--.5 min 12--.5 min 13--10 min 1 4 - 2 min 15--2 min 1 6 - 2 min 17--2 min 18--5 min 19-- 5 min

3) Drain time above each process tank averages 15 seconds. 4) Production rate is 12 barrels per hour.Plating thickness is 0.0002", protected by a clear

chromate. 5) Bath formulations are as follows: Soak cleaner Blended alkalies Surfactant Deflocculant Inhibitor By analysis:

90 g/l 5g/l 2g/l 3gfl

PH Temp

>11.0 160" F.

4

TEXT FOR OVERHEADS Figures 1-5 Electrocleaner Blended alkalies Deflocculant Inhibitor Foam suppresant

9ogn 2gn 3gn 18/1

By analysis:

Free NaOH PH Temp

30 g/l >11.0 160" F.

Hydrochloric acid Temp

30% by volume Room

Cvanide zinc Zinc Oxide (ZnO) 45 gn Sodium Cyanide (NaCN) 100 g/l Sodium Hydroxide (NaOH) 50 gA By analysis: Zinc Total cyanide

35 gn 102 g l

Total NaOH 95 8/1 PH >13.0 Temp 70-85" F. Cautions: Contamination with chromium or nitrates results in poor adhesion Contamination with copper, cadmium or lead results in dark deposits Hazy deposits result from organic contamination or poor rinsing Staining in storage results from poor rinsing

5

TEXT FOR OVERHEADS Figures 1-5 Clear chromate Chromium as ~ r + 6 as Cr+3 Sulfate Inhibitors PH Temp

30 g/l 4g/l

3. g/l 1.0

80' F.

Fip. 5 Cyanide zinc barrel plating line--modified rinsing system 1) Tank 3 reduced to 3 gpm input, and Tanks 6 and 7 to 1 gpm. Flow restrictors installed on input line (non-adjustable). 2) Tanks 10 and 11 converted to two-stage rinse.

3) Tanks 12 and 14 converted to drag-in/dragout system (77% recovery of plating chemicals). 4) Tanks 15 and 16 converted to two-stage rinse, total input of 0.3 gpm. 5) Tank 17 converted to strip tank (removal of accumulated metal from equipment; non-process step). 6) Air spargers added to all rinse steps. 7) Conversion to deionized water for all process steps. 8) Plating chemical losses reduced from 1280 lbs/yr zinc to 294 1bs.yr zinc; 1477 Ibs/yr cyanide to 340 Ibs/yr cyanide 8) Total cost for water, lost chemicals and water pollution control reduced from $17,843/yr to $8,580.

PROCESSES FOR PLATING ON ALUMINUM Chrome Decorative Chrome Protective 3

Decorative Chrome

I

I

I1 Alkaline clean/rinse X X Acid didrinse Act i v a t e / r i n se Ix X Zinc strike/rinse X C o m e r strike/rinse X Copper/rinse Nickel/rinse X N icke I/ri n se C h r o me/ri nse X Z i n c / r i n se Chromate/rinse

X X

Ix X

X

X X ~

-~

X X

X X X

~~

I

Decorative Chrome Decorative Chrome I Basis for Coating

I

Alkaline clean/rinse Acid didrinse I Activate/rinse

l~~.alyze/rinse

Electroless deposit/

1 X X

It

Ix

2 X X X X X

I Basis

X X

for Magnetic Coating X X

X

X

Ix

(x

Ix

Ix

X

X

CoDDer strikdrinse

I NickeVrinse Nickel/ri nse C h rome/rinse

Ix X

Zinc

X X X

1

I

PROCESSES FOR PLATING ON STEEL

r--

d

i

Dec. Dec. Chrome 1 - C h r o m e X Alkaline clean/ X

rinse Acid dip/rinse Copper strike/ rinse Acid dip/rinse Co pper/ri n se Semibright - n i c k e l / r i n se Bright nickel/rinse Anodic treat/ rinse

1 ChromaWrinse

X

Ix

X

Clad X I

Ix

IX

X X

X

X X

X

X

X

X

I P r o t . IP r o t .

1 Copper

Chrome X I

X

X

I Zinc/rinse

1 Hard

Zinc 1 Zinc 2 X X

‘ I

Ix

I

Ix

PROCESSES FOR P L A T I L i)N ZINC DIE CASTINGS

Alkaline clean/rinse Acid dip/rinse Copper strike/rinse Copper/rinse N ickel/ri nse An odic t reat/r i nse C hrome/ri nse Chromate/rinse

Decorative Chrome Decorative Chrome Protective 1 2 1 X X X X X X X

X

X X -

X X

X

X

-

Finish

Protective 2 X X

Finish

X X PROCESSES FOR PLATING ON BRASS

-

Chrome

Alkaline cleanhinse X X Acid dip/rinse X C o m e r strikelrinse Acid dip/rinse C o pper/ri n s e IX NickeVrinse X C hrome/rinse -

1

Decorative Chrome Decorative Chrome Protective 1 2 X X X X X X X X X X X X X X ~

.-

Nickel

I