Anodizing - part 2

Heating things up

All of the chemicals I purchased online at Caswell Plating have their own specific temperature ranges for best results, so it is crucial that I be able to accurately control the heating of the different solutions I’ll be using. My best option for this task is to rely on a PID (Proportional Integral Derivative) temperature controller.

PID testing

Since I have never used one of these units before, live testing on some benign substance was imperative before I started messing with acids, so I filled one of my buckets with 4 gallons of water and started with one of the eBay Chinese 1500W/120v heaters.

Test #1: 120V 1500W (12.5a) heater, in plastic lid. This had the advantage of being able to use a regular 15a outlet. 

Original setup with plastic lid

Unfortunately, the water temperature never got any higher than 140℉ at the top, remained in the 50s at the bottom, and it took over an hour to do so. Unacceptable! 

I need MORE POWER!

Test #2: 240v 4500W (18.8a) heater, in plastic lid. I disconnected my air conditioner, and hooked the heater up to the 20a outlet. 

One 240v/4500W heater flanked by two 120v/1500W Chinese heaters

HOLY CRAP! That’s some power! The bucket was glowing orange from the part of the element sticking out of the water. The experiment was terminated after melting the lid, and briefly getting electrocuted once or twice.

This plastic is obviously out of its league

Unfortunately, this heater died an early death, possibly due to overheating of the parts sticking outside of the water (the ones glowing), and I was unable to do any further testing with it. 

Obviously, there is a definite need to keep these things as submerged as possible. 

Test #3: I decided to double up on the Chinese heaters, even though I knew my electrical system might not be able to handle it. Using two 1500W heaters at 120v would draw 25a, more than my 20a well pump outlet could supply, but I irresponsibly decided to try it anyway, relying on the circuit breaker to prevent burning down my house. 

Stupid… I know.

Anyway, I fabricated a steel holder for the two heaters, as not to melt any more plastic lids. This holder allowed the shorter heaters to be nearly fully submerged without touching the bottom of the bucket.

A CNC mill comes in handy in so many ways!

These heaters will need to get further down into the water (not in photo)

Fabricating an improved heater support

Splendid!

This actually worked great... initially. 

When the circuit breaker started tripping, and the electrical cords became warm to the touch, I decided to put an end to this madness before I burned the house down for real.

It started to look like doubling the voltage, ergo halving the amperage, was the only real way forward (that would explain why there are so many more 220v units for sale). 

So, back to the store I went. This time to pick up a 220v 3500W, and a backup 220v 4500W. Both of these heaters extended the same length into the water as the eBay ones, about 10" (25 cm), compared to the now defunct 13" (33 cm) long one.

If these don't work, it's all over.

Test #4: I chose the 220v 3500W (14.6a) for this test, and it proved to be a good choice at last.

Capturing the beginning of the test, water temperature is 85℉ at the top (and bottom)

25 minutes later, I had 4 gallons of boiling hot water!

A little while later, we-are-smoking!

PID boiling 4 gallons of water

Temperature data for test #1, #4, and the newest 4500W unit (note test #4 started at 84℉)

One important side note, is that I used a long ruler once or twice in all of these tests to mix up the water, because the heaters create layers of different temperatures, with the hottest water near the top of the bucket, and the coldest near the bottom. 

This worked well with a bucket of water, but I wouldn't want to be forced to stir some toxic acids if I don't have to, so some device that agitates the water would be a definite advantage.

I have not figured out what to use yet, but you'll be the second to know when I do.