Dura®, Durachrome®, are trade names of Plating Resources, Inc. Copyright and all other World Rights Reserved, 1990, 1995, 2012.





The following photomicrographs shown the difference in deposits plated in a conventional bath and a Dura bath.

Standard Bath
Dura Bath
Deposit surface at 100 x magnification.
Coarse crack structure from high
internal stress with large nodules & pitting.
Fine crack structure provides better
oil retention, hardness, wearability and smoothness.

Cross Section at 400 magnification
Large deep cracks extend down to
base metal serve as pathways for corrosion.
The greater number and smaller sized microcracks provide better lubricity and corrosion resistance.

The Dura Bath Additives complies with Federal Specifications:

AMS 2406 BAC 5709 MIL-C-23422
AMS 2407 DOD-STD-2182 MIL-STD-1501
AMS 2438 MIL-C-7460 NAVSHIPS 0919-000-9010
ASTM B-177 MIL-C-20218 QQ-C-320

Dura Bath Properties outlines several Dura bath features.

Dura-3000 is a State-Of-The-Art process for High Speed-High Efficiency plating. It performs equally well for flash or heavy build-up work on either ID or OD’s. Dura-3000 provides faster plating speeds and improves deposit properties like hardness, corrosion resistance, crack structure and wearability.

The Dura-3000 bath plates at 35 % efficiency.
Standard baths are limited to about to 15% and other high-speed baths to about 25% efficiency.

The process is very user friendly, easy to control and inexpensive to operate.

50% Faster Plating Speeds (1.2-1.3 mils/hr. at 2 ASI).
Extremely Smooth & Very Bright Deposits.
Buffers The Bath For Reduced Pitting & Noduling.
72-74RC Hardness, Better Micro-Cracks & Wear Life.
Maintains Speed Even As Impurities Increase.
Anodes That Stay Active & Last Longer.
Avoids Barium Treatments From Sulfate Break-Down.
Non-Etching In Unplated & Low Current Areas.
Used With Inexpensive Generic Chromic Acid.

Plating Speeds:
The high efficiency of this bath provides an approximate 50% increase in plating speed. Typical deposition rates for relatively clean baths are:

2 ASI 0.00125”/hour
3 ASI 0.00188”
4 ASI 0.00250”

This bath is much more resistant to the effects of impurities like trivalent, copper and iron than other high efficiency baths are. As such, the plating speed doesn’t slow down as much or as fast. Baths with extreme impurity levels, however, will likely be around 0.0002”/hour slower than the ideal rate, depending on the voltage & current density used.

Bath Control:
This bath can be used with chromic acid levels of 20 - 50 oz/gallon and sulfate ratios of 80-140:1. The best throwing power is achieved at a 120:1 ratio. Typical impurities such as trivalent, iron, copper and chloride should be kept within the recommended range for best bath performance. Porous pots, used with CR-3 Reducer, are effective in controlling impurities.

Item Optimum Range
Chromic Acid 30.0 oz/gal. 20 - 50
Sulfate 0.25 oz/gal. (by ratio)
Ratio 120:1 80 - 140:1
Dura-3000 & 3500 (see below)  
Trivalent Cr 1 % of chromic acid 0.70 - 2.50 %
Metallic Contaminants < 5.0 g/l  
Chloride < 20 ppm  
Insoluble’s < 0.04 g/l  
Temperature - F 140 130 - 150
Current Density 2.0 ASI 1 - 10 ASI

The equipment normally used for hard chrome plating is satisfactory for use with Dura-3000. Typical tank linings like PVC, Koroseal or molded HD polyethylene are best. While lead linings can also be used they are not recommended due to their conductivity. Conventional anodes and rectifiers are used. Although not necessary, it’s best to use rectifier(s) with a 9-12 volt output, especially for baths with high impurity levels, and with a maximum of 5% ripple at the actual voltage used. The tank should be ventilated and PVC systems are commonly used. The heating and cooling systems should be of either titanium or Teflon construction with controls to maintain the desired bath temperature. Mild air agitation is desirable for mixing in chemical additions and avoiding temperature stratification in deep tanks. The air agitation should be provided by a low pressure blower and controlled to avoid excess chrome mist. Pumps, filters and plumbing should be schedule 80 CPVC with glued fittings.

Bath Additives:
This bath uses either the Dura-3000 Additive or Dura-3500 Booster for conversions and maintenance, depending upon the bath type. While analysis may be used, the Dura levels are best controlled by the plating speeds obtained.

Dura-3500 Booster
This powdered additive is used to convert standard hard chrome baths to High Speed High Efficiency usage. Dura-3500 Booster provides a drastic improvement in bath performance and plating speed. Do not add Dura-3500 Booster while plating; always add it when the tank is empty of work. Sprinkle the addition evenly into a hot bath and agitate until fully dissolved.

The Dura-3500 Booster is normally a one-time addition that's only used for the initial conversion. But because of variances in anode ratios, current densities and amperes per bath gallon, an occasional small addition of the Dura-3500 Booster may be needed for some applications. We suggest that you have the Dura-3500 level tested annually.

One Caution
Do not add the Dura-3500 Booster to baths that plate parts with highly stressed base metals or those with surface hardness exceeding 45 RC, without first stress relieving the parts by baking and then shot peening prior to plating, see QQ-C-320. This is especially important for deposits thicker than 0.001” because the base metal stress can transfer to the chrome deposit causing macro-cracking, and in severe cases a loss of adhesion, especially after grinding.

The only downside for not using Dura-3500 in these baths is a slightly slower plating speed. You should, however, still use the Dura-3000 Additive.

Dura-3000 Additive
This liquid additive is used to convert other high efficiency baths. It’s also used for bath maintenance once a bath has been converted.

Bath Conversions:
Conversions to this process are easy and inexpensive.

Standard Baths
These baths are converted by simply adding 2.5 oz/gal. of the Dura-3500 Booster.

High Efficiency Baths (others)
These baths are converted by adding 3% by volume of Dura-3000 liquid. The Dura-3500 Booster is not normally needed, unless the catalyst level is low.

High Fluoride Baths
High fluoride baths should not be converted to this process.

Bath Maintenance:
As with any hard chrome process, the bath should be tested for its chrome, sulfate and impurity levels on a regular basis, the frequency is based on maintaining them within acceptable limits. If needed, Plating Resources, Inc. laboratory can provide this service along with recommendations and guidance for controlling bath impurities.

Dura-3000 Liquid Additive is added to maintain the Booster level in the bath.
These additions can be based on either ampere hours or chromic acid consumption. Regular additions of Dura-3000 will eliminate variances in plating speed and provide for more consistent deposit quality. The maintenance addition rate should be:

1/4 gallon per 100,000 ampere hours plated, or

1 gallon per 100 pounds of chromic acid consumed.

Regulations & Fume Suppressants:
All chrome plating solutions produce misting during operation. This mist contains Cr(VI) which is regulated by the EPA for environmental and OSHA for worker safety issues. Be sure to follow all federal, state and local regulations for safe operation and hazardous disposal. Fume Suppressants like FS-600, FS-750, FS-900 and Cancel ST-45 are very effective in controlling Cr(VI) misting. These low cost – permanent type fume suppressants are compatible with the Dura-3000 bath and do not break down to cause contamination or pitting.

Dura-3000 and Dura-3500 Booster are used in baths that contains chromic acid and sulfuric acid. These are all industrial strength chemicals and must be handled carefully and in accordance with the directives provided in the individual MSDS forms.

Read and understand the MSDS on all of these chemicals before handling or using. Ensure that all regulatory standards are followed and limit personal exposure as required for Cr(VI) by OSHA.

Avoid personal contact with these chemicals, avoid splashing and avoid breathing any fumes released during operation. Do not inhale any dust, mist or vapors from these chemicals. Do not allow these products to contact the skin or eyes. In case of contact, flush immediately with large amounts of fresh water and seek immediate medical attention.

Wear protective clothing such as aprons, gloves, face masks and respirators. Be sure that adequate eyewashes and emergency showers are available nearby before handling or using any of these chemicals.

Designated work clothing should be worn while using these chemicals and the worker(s) should thoroughly shower and change into fresh-clean street clothing before going home. Decontaminate all work clothing before reuse.

The user is responsible for providing adequate work clothing, personal protection, limiting personal exposure, providing any required clean-up, decontamination as well as any needed medical attention.