HENE L - 600 Hard Chrome Plating
HENE L - 600 is a new generation Hard Chrome plating process which is far superior to both conventional and mixed catalyst bath. The make-up and maintenance chemicals are well balanced and are in liquid form for easy maintenance.
HENE L - 600 has several distinct advantages over the earlier hard chrome plating process and are enumerated below:
- Higher Cathode efficiency 23-26% resulting in saving of expensive electrical power by 30-40%.
- Increased Wear Resistance by 20-25% results in longer life of the plated compounds.
- Produces microcracked deposits (600-1000 cracks per linear cm) resulting in better corrosion resistance.
- The constituent of the bath is easy to maintain as the chemical products used are well balanced and are in liquid form.
- Bath operates satisfactorily within a wide range of operating parameters without affecting the deposit characteristics.
- Wide cathode C. D. operation 30-60 A/dm2.
|Bath Make-up ||Optimum ||Range |
|HENE L - 600 Make-up ||500 ml/l ||450-550 ml/l |
Note: It is recommended to take the required amount of HENE L - 600 make-up to the tank (where the final solution is to be made) and add the DM water until the density of the solution becomes 21oBe.
| ||Optimum ||Range |
|Density ||21o Be ||20 - 23o Be |
|Temperature ||55o C ||52 -60o C |
|Cathode Current Density ||50A/dm2 ||30 - 60 A/dm2 |
|Anode Current Density ||17.5 A/dm2 ||15 -22A/dm2 |
|Voltage ||6 ||4 - 12 volts |
It is advisable that for getting hard chromium deposits, the current density and temperature both are maintained at optimum levels, although HENE L - 600 process gives consistent quality results with wide operating conditions.
The base metal surface has to be smooth and uniform and surface imperfections are to be removed by mechanical polishing and burnishing operations.
The components to be hard chromium plated should be pre-cleaned in suitable hot alkaline soak cleaner and rinsed well. To ensure good adhesion of hard chromium deposit on mild steel component, anodic etching in conventional chromic/sulphuric acid bath at 50o to 65o C for 30 secs. - 120 secs., should be carried out in a separate tank. The parts should be transferred into the plating bath without rinsing. After plating, the parts should be dipped in drag-out tank, neutralised, followed by water rinse and hot water rinse.
The HENE L - 600 chrome solution preparation is very simple and is as under:
- Fill the cleaned plating tank with D.M. water to almost onethird of the operating level.
- Add the calculated quantity of HENE L - 600 Chrome make-up solution with stirring. The solution should be added in small quantities with continious stirring.
- Add DM water with constant stirring until the density becomes 21o Be which will maintain the working level and stir for another 2-3 hours.
- When the solution becomes homogenous, heat the solution to 55o C. Place the anodes and electrolyse the bath for 3-4 hours at operating temperature of 55o and at a 2 c.d. of 35-45 amps.dm2.
Chlorinated, flexible PVC lined mild steel tanks are suitable. Lead lined tanks are not suitable and if the tanks are lead lined, they should further be lined with flexible grade PVC.
The plating tanks should be equipped with a suitable heating device and thermostat control to maintain the temperature within the specified range. Suitable exhaust system with scrubber facilities should be provided to keep the environment clean. Cooling is required to control the temperature of the solution since heat is evolved due to higher voltage and operating current. For direct heating and cooling, titanium coils are normally used. PTFE or PVDF coils are also suitable for heating and cooling.
The anodes should be 7-10% tin and 93-90% lead alloy. Round anodes are normally preferred as compared to flat type. However, the life expectancy of tin-lead alloy anodes are comparatively less than in conventional chrome plating solution. When the bath is not in use, anodes must be removed. Lead-Tin-Silver (93:6:1) anodes have longer life than lead-tin anodes.
Platinized titanium anodes can also be used. But care should be taken that these are completely covered with lead dioxide film (brown black layer).
A direct current source at 6-12 volts depending on the current density requirements is suitable for use with HENE L - 600 Hard Chrome solution. The rectifiers used s hou ld be of 3 phase rectification, preferably with oil cooling and provided with stepless voltage control between 0-100%. The residual ripple must be below 5%. The current carrying capacity of all electrical connections, busbars and plating jigs must be designed to carry the required amount of current continuously.
The solution should be analyzed regularly and maintained as under :
|Chromic Acid ||: ||250 - 350 g/l |
|Sulphate ||: ||2.25 - 3.9 g/l |
The solution concentration can be maintained on the basis of hydrometer reading and the solution density can be maintained by regular additions of HENE L - 600 Maintenance. We do not recommend the use of commercial grade chromic acid for maintaining the solution density as this will change the balance of chromic acid and special catalytic addition agents.
To increase the chromic acid add HENE L - 600 Maintenance.
To increase the sulphate content, add calculated amount of A.R. Grade Sulphuric Acid and to reduce use A.R. grade Barium Hydroxide.
To increase 1 g/l of chromic acid, add 2 ml/l of HENE L - 600 Maintenance.
We do not recommend any addition of Chemicals other than specified in this instruction manual, as this may adversely affect the performance of the bath.
TABLE I -- PLATING SPEEDTime in minutes to deposit 1.0 Micron (Average)
|Current Density ||HENE ||Conventional |
|A/dm2 ||(Mins) ||(Mins) |
|20.0 ||4.8 ||7.7 |
|30.0 ||2.2 ||3.6 |
|40.0 ||1.6 ||2.6 |
|50.0 ||1.2 ||2.1 |
|60.0 ||1.0 ||1.8 |
DISCLAIMER: Our recommendations are made in good faith and are based on our skills. However, since the conditions of use of these products are beyond our control, this information is given on the express condition and agreement that Grauer & Weil (India) Limited, will not be liable to any person by reason thereof. Nothing herein shall be deemed to be a recommendation to use any product in violation of any existing patent rights.