Summary for brass v-block overheating Discussion
Brass v-blocks overheating during chrome plating is the central issue in this thread. Sanjeev Kumar of Gujarat, India says his hard chrome line plates plungers/pistons at 35–40 A/sq.dm for 20 minutes, with about 4500 amps passing through brass V-blocks, but the blocks still heat up despite water cooling. In reply, the answerer says the cooling-water temperature probably is not the main factor as long as flow is sufficient, noting that water cooling is used successfully in very hot industrial applications. He suggests several practical checks: reduce current somewhat if plating quality allows, since a longer cycle may be acceptable; make sure the V-blocks have not been weakened by excessive drilling for cooling channels; confirm whether bussing is from both sides of the tank; and inspect the temperature of the bus bar feeding the blocks. He also asks for photos to better diagnose the overheating cause.
Quickstart:
Alligator clips are generally not used when doing production plating. Rather, the workpieces are hung on plating racks which, in turn, are hung on a copper or brass bar which spans the width of the plating tank plus a few inches, and this ‘work bar’ sets in V-shaped ‘saddles’ mounted on the rim of the tank and bussed to the rectifier.
Q. Sir, we have a hard chrome plating plant. We have a product named ‘plunger/Piston’. We are using current density of 35-40 Amp/sq.dm, having a 20 minute process time. Overall current passing is 4500 Amps for 20 minutes through Brass V-blocks. The problem is, we are often facing V block heat up in spite of using cooling water through it. Can we know what temperature water should be for v-block cooling?
Sanjeev Kumar
– Gujarat,India
August 7, 2025
A. Hi Sanjeev.
There is nothing wrong with the water cooling idea — it’s even used on the continuous casting molds for steel manufacturing at very high temperatures, and I don’t think the water cooling temperature matters a lot as long as the flow is sufficient.
However, firstly you may be able to reduce the current a bit without bad effects on your plating, at the cost of a few minutes more of plating time.
Secondly, I suppose it’s possible that you have drilled so much for water cooling channels that the v-blocks don’t have enough meat left on them.
Thirdly, are you bussing from both sides of the tank?
Fourthly, how’s the temperature of the bus bar feeding the v-blocks?
If you can send a pic and a description of these v-blocks to finishingdotcompublic@gmail.com for posting here, it may be possible to quickly surmise the cause of the overheating.
Luck & Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com – Pine Beach, New Jersey
Need quick confidential answers? $25
Need project assistance? $100/hr.
A. Hi Sanjeev.
As I found on some site on the web, electrical conductivity of brass is only fourth of pure copper. Try to change your brass V-blocks to copper. And check your busbars also.
Good luck
Alex Sirota
Plating Engineer – Lod, Israel
September 21, 2025