Dura®, Durachrome®, are trade names of Plating Resources, Inc. Copyright and all other World Rights Reserved, 2014.

 

 

 

DURA BATH PROPERTIES

Bath Comparison

Bath Type
Standard
Dura-60
Dura-100
(Fluoride Bath)
Dura-2000
Dura-3000
Plating Speed
0.0007”
0.0008”
0.0012”
0.0009”
0.00125”
Throwing Power
Poor
Good
Fair
Very Good
Excellent
Efficiency
15-16%
24-25%
32-33%
26-27%
34-35%
Brightness
Fair
Good
Excellent
Very Good
Excellent
RC Hardness
56-60
66-68
70-72
68-70
72-74
Wear Resistance
Fair
Good
Excellent
Very Good
Excellent
Crack Type
Macro
Micro
Ultra-Micro
Micro
Ultra-Micro
Crack Density
50
950
8,500
2,000
3,000
Corrosion Resistance
2-8
15-20
35-40
20-30
25-35
Etch
0.06
0.04
0.11
0.07
0.02
Impurity Build-Up
Low
Low
High
Low
Low
Impurity Resistance
Poor
Fair
Medium
Good
Very Good
Bath Cost
3.1
4.4
4.7
4.5
7.3
Profitability
Low
Fair
Good
Good
High

Notes:

1) The Dura-3000 bath, even with the higher initial cost, provides the fastest pay-back and monthly profitability because of its faster speed, better quality deposits and ability to handle impurities.

2) All of the Dura baths can be used at low concentration for fresh bath make-ups which saves considerably on the chromic acid cost.

3) Bath cost is a function of the ingredients used and their concentration. This is shown in a scale of 0-10 to eliminate normal chemical price variations. Consider bath costing as a one time investment while higher efficiency produces more work over the long term.

4) Plating speed is in inches per hour (per side) at a current density of 2 ASI, from baths with normal impurity levels. The throwing Power of baths can be increased with the use of conforming anodes. Efficiency refers to the amount of chromium deposited per unit of DC electricity.

5) Crack type & density refers to the normal macro-micro cracking of a chrome deposit. Macro-cracks are large & wide and frequently extend down to the base metal. These are detrimental to corrosion and wear resistance. Micro-cracks are much smaller and tend to be in layers which don’t extend to the base metal. As such, micro-cracks provide much better deposit properties and oil retention.

6) Corrosion resistance is the typical hours of 5% salt spray resistance, per ASTM B-117, on #4140 TG&P rods with a 0.001” deposit. Corrosion resistance is very much dependent upon the crack pattern type & density and the degree of base metal finish and preparation.

7) Etch refers to the amount of low current density etching that can occur without stop-off in unplated areas. It is shown in grams/hour weight loss per sq. inch of surface on #1010 steel at 2 ASI. This is not a concern if the entire part is plated or if stop-off is used. Otherwise, low current density etching can increase impurities like iron. Numbers below 0.06 are not of concern, while 0.07 and above may slowly attack bare aluminum. Numbers above 0.10 are quite aggressive to all metals.

Dura Additives
The Dura baths are designed for use with regular (generic) chromic acid so there are no expensive proprietary blends to buy. This allows you to tailor the bath to your specific requirements while also greatly reducing your costs. The Dura baths are “User Friendly” and very easy to control.

The Dura Additives improve the chrome baths performance. Routine maintenance additions of the Dura Additives should be made to keep them at their optimum level, as shown in our technical literature. These additions can be based on either ampere hours or pounds of chromic acid consumed. Periodic analysis by Plating Resources, Inc. will show if a minor adjustment is ever needed.

Physical Properties
Following are the typical physical properties of the Durachrome baths, along with related chromium data.

Cr Atomic Number: 24
Cr Atomic Weight 51.996
Density ( S.G.): 7.19 grams / cc
Crystal Form: Body Centered Cube
Melting Point: 1875 deg. F.
Magnetic: Paramagnetic
Heat Conductivity: 0.165 cal./cubic cm. @ 18 deg. C.
Resistivity 13.1 - 19.3 microhms / cubic cm.
Wear Factor: 2.0 Taber
Coefficient Of Friction: Steel - 0.14, Babbit - 0.10
Coefficient Of Expansion: 8.0 - 8.5 x 10 (-6)
Internal Stress: 5,000 - 20,000 psi, compressive
Hardness: Up to 74 R.C., depending on bath type.
(standard chrome is only around 56-60 R.C.)
Adhesion Strength: 125,000 psi
Fatigue Limit: 85,000 - 90,000 psi
Chromic Acid: CrO 3 - 52% chromium metal. Also known as Chromium trioxide. The valence is 6, technically not an acid until dissolved in water. Consumption is 0.0004946 pounds per mil. sq. in. plated, with no losses. Use a factor of 0.0006 for typical losses.