The authoritative public forum
  for Metal Finishing since 1989
-----

Stoddard in the plating tanks

I run a small anodize department in our aerospace division. The anodizing department is completely walled in from the rest of the facility. While I was away, a decision was made to put a stand alone power flush in the anodize department. It runs 143 deg. flash point stoddard solvent.It is located about 15 feet from the chromic anodize and about 30 feet from the hard coat line. After the parts are flushed, they are removed from the unit and blown dry with shop air. Does this provide a fire hazard for me? Will the stoddard solvent settle on the tanks and contaminate them? Will the stoddard mist over and coat the racked parts? Will a partition decrease or remove these possibilities? I am afraid that the solvent will contaminate either the surface of the parts or the solutions in the tank.

Tracy Miller Cheatham
AlliedSignal
1997

---

1998

Yes. and see The Oil Diet for a reference to the use of oil in a plating facility. Standard practice is to keep oils and solvents away from water based solutions to prevent problems of miscibility. The new device may not cause a problem in the anodize tanks, but blowing solvent around with an air gun is always a problem, because we all get careless when we get busy, or start horsing around. Do you use a low pressure blower for agitation of any of your tanks? The intake of solvent into the blower would be very poor practice. I would also worry, as you mentioned about settling of a mist onto the tank surface.

I would have to check with the safety department about the fire hazard, and the safe use of the machine. I am sure that there is a Threshold Limit Value on Stoddard solvent which would be difficult to measure when it is blown dry with an air hose. The way to test it would be to install collectors on the operators for several shifts, but these tests are easily misleading. There must be a 21st Century way.

  
Tom Pullizzi
Falls Township, Pennsylvania

About this Stoddard mist: I know that organic solvents leave a residue only after immediately being flushed with air. I had an experience in college with cyclohexane where a student (not myself) dried a beaker that had a small amount of cyclohexane residue in it. He/she used the lab air jet, and then placed the beaker in an oven to dry further (this person was obviously confused by our teacher's instructions). A few moments later the oven exploded open spewing flames out and up 6 feet. Luckily it was just a flash fire that was easily put out and only scorched the surface of the oven and wall, but those flames were still dangerous. I realize that drying these parts quickly is important, but it would seem safer to use dry cloths to absorb the excess Stoddard solvent, preventing any mist. At least this way you'll know exactly where the flammable solvent is, instead of it being misted over the entire shop. However after a few minutes, I'm sure the fire hazard the mist created w!ill no longer be present.

Melissa Mele
General Electric
1999