Hello,
My name is Şevket from Turkey. I am a production manager in a factory which manufactures engine valves. My problem is about the hard chrome plating for the surfaces of valves. We are plating hard chrome for ten years. And now we improved our technology with a new system. In this system first of all we are sinking the valves to clean the surfaces from oil and the other unwanted materials in the caustic bath with the opposite current. And then sinking to the other two baths including water. After that we send them to the chrome bath which includes chromic acid and sulfuric acid. I see that the stem part of the valve is burned and there is no clear appearing on the surface. If i decrease the current then it doesn't clear valve. When i use normal current for caustic bath the same problems repeat. Expecially the tips are burning, the middle of the stem surfaces are clouded or mat. which amper must i work for cleaning and chrome plating. What are the suitable chemical materials for the plating.
The temperature is nearly 45 for cleaning and the current is 1000 A for 96 valves and their area is 0,2 dm2 for each valve cleaning ın 180 seconds.Redresor voltage is 5,5-6V.
For the chrome tank the temperature is 65 and the current 1200 for 96 valve and the surface area is 0,2 dm2 for each valve. The time is 10 minutes. Redresor voltage is 4V
Is my method suitable for chrome plating or not and what must i do?

Hi Şevket

to the Surface Engineering Forum.

My knowledge of the hard chromium electroplating process is limited, so I hope someone else here can give you guidance.

The following links should provide some reading and may help.

http://www.pfonline.com/articles/0203qf2.html

http://www.pfonline.com/articles/pfd0517.html

http://www.pfonline.com/articles/pfd0016.html

http://www.pfonline.com/articles/0504qf1.html

http://www.pfonline.com/articles/0704qf1.html

Thank you very much for your interest Mr Gordon. Your advise helped me.