VINEGAR AS A DE-SCALING AGENT

by Albin Drzewianowski

Lately I have been experimenting with VINEGAR as a method to clean fire-scale off of forged ironwork, before putting a final finish on the item. I am very pleased with the results. The down side to this system is that you have to schedule in something like 3-5 days for the vinegar to “do its thing”. Given my habit of “just in time production” i.e. finish the trade item on Saturday midnight before the monthly meeting, this does not always work out. But if you plan ahead and include time for the vinegar to de-scale your work, it saves a lot of time spent with the wire wheel and does a better job.

Vinegar is a very mild acid, acetic acid. It does not work fast, but neither does it pit the work like some other acids might. As you use the acid, it gets weaker and weaker. It still works, but takes longer. A major plus is that vinegar is relatively cheap. I buy the white vinegar in the gallon jugs at the super market.

There is an investment here. You need to accumulate a number of different size plastic containers. For small pieces, I have a couple of different size Tupperware containers. For large pieces, I have a Stearlite plastic container meant to store clothes under the bed. It is about 4” high and 20” by 14”. I found that I needed a long narrow container for de-scaling roasting forks, ladles, fireplace pokers, etc, so I bought a piece of 4” PVC pipe, cut a piece about 28” long and then glued (using the appropriate cleaner and cement for PVC pipe) a cap on one end and a screw cap on the other (all parts available from you local box/hardware store). Unfortunately, it does not stand upright by itself, so I keep it in a 5 gallon bucket. You need to be creative to find containers that will allow you to submerge your ironwork in the vinegar.

Once I have put ironwork in the vinegar, I agitate it every once in a while. Also, I am told that it works better if the vinegar solution is hot. So in the future, I will be experimenting with that also.

It has been reccemended that even with vinegar, you should rinse in a neutralizing solution, not just plain water. So I have added an additional step to my process: After taking the ironwork out of the vinegar solution, I rinse it in a baking soda solution first and then in clean water.

You need to dry immediately or it will start to rust. I wipe dry with a rag and then use a heat-gun to drive all the moisture off the steel.

This process leaves a film of ironscale on the steel. Wiping the steel dry with a rag, gets most of it off, then I use a Scotch Brite pad to get off any remainnig. This process leaves a bright "satin" finish to the steel.

When I am finished de-scaling, I filter the vinegar to get out the flakes of scale that remain. I figure if you leave in the flakes of scale, the vinegar will continue to eat away at them, leaving you with weak vinegar. So I use a large funnel lined with a paper coffee filter, when pouring the vinegar back into its storage container. This is a slow process, but I think it lengthens the effective life of the vinegar.

Rumor has it that this vinegar which has been in contact with iron/steel makes a great stain for oak wood. I have not tried that yet, but have set some aside for a later experiment.

SAFETY ISSUES: Always wear eye protection, even though this is just vinegar, it is still an acid and you don’t want any in your eyes. Also, it is a good idea to wear rubber gloves. When the acid is "worn out" then add some baking soda to neutralize it before discarding. Becareful adding the baking soda, if you add to much baking soda to the solution at one time, it will foam up and overflow the container (remember the "volcano" science experiment from elementary school).

-- AlbinDrzewianowski - 08 Jan 2008

• Possible improvement to the process: I was at the 2009 Furnace Town Blacksmith Guild Hammer-In and the featured demonstrator, Johnathan Nedbhor suggested adding a little salt to the vinegar, about 1 tablespoon per gallon. This increased the number of free ions in the solution and thereby did a better/faster job of descaling. -- AlbinDrzewianowski - 12 Apr 2009