Sunday, July 3, 2011


It's in your multivitamin. And I've been trying to get my steel columns coated with it. Zinc is applied in a variety of ways to raw steel to keep it from rusting. I've already had some of my steel connectors "hot dipped galvanized" - the ones that will be outside, set on top of the brick columns of the courtyard to bolt the roof structure to. Hot dipping is the most protective way to apply zinc; the steel is dipped into a kettle of the molten stuff, leaving a thick layer on the surface. Especially in this corrosive coastal environment, steel left outside better be either stainless, painted (regularly), or hot dipped. Of course for me painting is out, and stainless steel is ridiculously expensive. So the decision to hot dip my exterior steel connectors was easy.

What proved to be a much more difficult decision is how to finish the 22 steel columns and four steel connectors that will be inside the house. These will be mostly visible, like the connectors outside, but they will not be exposed to the weather. So my first thought was not to finish them at all; just let the raw steel show. Then I saw them in the welding shop and they had a grey coating (which I learned is called "mill scale" - a byproduct of the forging process) and black letters stamped on them. I was hoping for a uniform bright silver. The welder said that to get that look the columns would have to be sandblasted; that would remove all the mill scale and lettering. But then, he said, they would corrode so fast there would be rust on them before they even got to the site. And even if they somehow made it through transit without rusting, they would have to stand out in the weather for weeks before the walls and roof are completed around them. No way would they survive the humidity and salty air for that long without some kind of protection.

Still, they don't need the level of protection offered by hot dipping. Besides, I had seen some examples of hot dipped steel in the welder's shop, and the zinc was not very uniform; there were streaks and drips, lots of variation in the way the zinc formed and hardened. At least for my interior steel I was looking for something cleaner and more uniform.

So. My search began. The welder mentioned "powder coating" as an option, and gave me the name of a company in town that does this. The process puts a very thin layer of clear (or colored) plastic on the steel. The steel would have to be sandblasted first to get the mill scale off, which would be over $2,000. Still, I liked the idea of an invisibly thin clear coating letting the silvery steel show. But I don't like plastic. In particular I was put off by the idea that I would be able to see the steel but not touch it; it would look like steel to the eye but feel basically like vinyl. If I see the steel I'll want to feel the steel. Also I started to worry about the long-term durability of this micro-thin plastic coating, and what if just a spot of rust occurs prior to its application. Then there's the cost of this process, whatever it would be, over and above the sandblasting cost.

Next? How about "electroplating"? I had heard of this before when specifying hardware - some is hot dipped with zinc and some is electroplated with zinc. The latter provides a much thinner layer of zinc, and is junk around here - IF the hardware is outside long-term. But could electroplating be just the amount of protection I need for my columns during transit and installation? And because of the thinness of the layer, perhaps it would give the uniform finish that I'm going for.

I looked up companies that do electroplating. None in town. Two in Raleigh - two hours away. I called and talked with people at each on several occasions and eventually became confident that this was the perfect finish for my columns. So I sent them my steel drawings and got a cost estimate from each. One was substantially lower than the other. I arranged with a representative at that company to drop off the steel. I rented a van, and we loaded it with 2,900 pounds of steel:

When I got to this company in Raleigh they had me back up to the loading area. I opened the back doors, and they looked surprised. One said something like, "We never do stuff like this." So they paged the rep I had been speaking to over the past few weeks about this job and in the meantime unloaded a few of the columns. When the rep came out and saw the columns he said, "I can tell you now that my estimate was too low." I raised my eyebrows and said, "Well, as long as it's close... ?" He looked back at the columns. After a few minutes as they unloaded more he said, "This is going to be $100 a column." That's $2,200. His estimate was $1,300. A friend of mine who rode up with me asked the question before I could: "Why was the estimate so low?" The rep said the columns are bigger and heavier than he thought. "But you had the drawings--" I said. "Yeah but I didn't know they would be 130 pounds each," said the rep. Every dimension of these columns was on the drawings; the length and thickness of tubing, the thickness and number of plates. There's your 130 pounds. If you didn't want to calculate it, you could have asked me - before giving me an estimate and inviting me to haul a ton and a half of steel 150 miles.

Of course I was aggravated (to put it in non-cussing terms), but since I had made the trip I was ready to negotiate with him on the higher cost. I didn't want to take advantage of his estimating error, and his "new" estimate was close to the other estimate I got anyway. But then he started to question whether they had the ability to electroplate these columns at all. He walked me to the tanks they use for this process. They are just large enough for one column to fit, and he said that because of that the zinc finish might not turn out very well. He said that the other company in town has larger tanks and may be able to handle this job. But the only way to tell is to run one through. So we agreed that if he would match the other company's estimate, he would take the job and try a column, and that if it turned out bad he would take them all to the other company.

The rep called me a few days later to say he had taken all my steel to the other company; his one-column test had failed. I assumed my columns would now be electroplated successfully. A few days later the welding shop called to let me know that the steel connectors for the courtyard had returned from being hot dipped. I went to pick them up and drop them off at the site. I was surprised at how good the zinc coating looked on them. They looked like they were dipped in silver.

I started to regret that I didn't just have the columns hot dipped as well. But I expected the electroplating would look great too. That very day - the day I picked up these connectors - I got a call from the second electroplating company. They said they ran three columns through the process; there's streaking and discoloration. The columns are just too big for electroplating to work. "Sorry, we can't do this job." I rented another truck, drove to Raleigh, got a very sore back loading every column with help from only one person the company would spare (a high school summer intern, from the looks of him), and drove back to Wilmington. My columns spent two weeks in Raleigh and returned exactly as they left. Well, except for the three that now have really bad electroplating jobs. Here they are before being unloaded back at the welding shop; the three in the center were electroplated, the rest still show the dark grey "mill scale":

Despite all this, I am more than a little excited that my only remaining option for these columns is hot dipping. Having seen the result of this process on the smaller connectors, I'm eager to have the rest of the steel done. So my columns are at the welding shop awaiting a truck that will take them to get dunked in a pool of molten zinc - in Charlotte. I think I will have the most well-traveled steel columns of any house in town. Okay, so it would be surprising if I don't have the only steel columns of any house in town.

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