Galvanizing 103

In the last installment, we looked a little at the broad range of cleaning technologies available to a galvanizer.  Picking the right one depends on both experience and a little luck!  If the customer can possibly tell you what sorts of cutting fluids, lubes, etc. they use, picking the right way to clean is simpler.  For example, if they only use a paint marker, and not much else, then there are at least 2 easy-ish ways to take it off---quick spray of paint remover, then a caustic or acidic degrease will likely take it off.

Usually, of course, the steel picks up stuff all they way along, from the steelmaker themselves, to the trucking, to the initial fabrication, to secondary fabrication and storage perhaps outside, then more trucking, and possibly sitting in the snow, rain,  wildfire smoke, flooding and mud, even saltwater.  At this point there could literally be hundreds of different things on the steel! 

So, what does a cleaner have to do to all of this crud to open things up for the de-rusting?  There are 4 basic technical terms used when talking about what a cleaner does to “clean”.

  1. Dissolution:  Chemically reacting with and destroying a soil (saponification by alkali, phosphorylation by acid degrease, simple dissolution by solvents)  OR with pickling, dissolving the iron/iron oxides.
  2. Displacement: Moving the soil away from the surface (may involve friction, agitation, and some chemical and surface tension effects)
  3. Emulsification: Tying up the soil to prevent it from re-depositing AND sometimes making it more chemically reactive for further breakdown.
  4. Dispersion: Making the emulsified soil particles very small, or in some cases further tying it up to force it to settle to the bottom or top of a dip tank.

It boils down to getting the soil to release from the steel, and get into any cracks or divots in the steel to get the soil out of them.  Then you can dissolve the stuff, or tie it up in tiny droplets, or in the case of blasting, blow it away from the work.  Many approaches combine some or all of these at once!

The most common method, and perhaps the easiest, is simply filing or grinding the area (if you can see and reach it.)  “Elbow grease” works well for visible and smaller areas.  Larger areas, again if it is accessible can be sand-blasted or wheel-blasted.  BUT it is easy to miss areas, you can’t get into small tubes for instance; and it leaves the surface rougher.  Roughness can pick up more chemicals later in the process; worse, it can pick up more zinc, and sometimes the grinder marks will even print through the zinc coating.  And there are also exceptions—some types of steel NEED a little rougher surface to help get coating weights up to specification!










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Galvanizing 108

By Robert Woods
May 07, 2021 Category: Galvanizing

BLOG 8-Robert M. Woods RINSING after DEGREASING So, now the soils are removed for the surface of the work---but there may still be a layer of chemical sticking to it. IF this is coming out of a caustic bath, a direct movement into an acid pickling tank, the layer can actually neutralize some of the acid, wasting it. IF this is coming from an acidic cleaner such as Hydronet, there is no neutralization; but any Hydronet remaining on the surface is also wasted. To remedy these issues, most operations will have a rinse tank after the degreasing tank, either caustic or acid-type. For the acid-type, the rinse can be used to make up for any drag-out or evaporation of the degreasing tankany dragged out degreaser is put back into the degreasing tank. For the caustic-type, the same make up occurs; and the rinse will prevent much of the neutralization of the following acid tank. Control of a rinse tank then makes economic and process sensesaving the more expensive chemicals and keeping subsequent

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By Jim Krimmel
April 27, 2021 Category: History

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Galvanizing 107

By Robert Woods
April 21, 2021 Category: Galvanizing

BLOG 7-Robert M. Woods Last blog was discussing a pure acid degreasing approach, using Phosphoric-acid based product such as Hydronet Base, Ricarica, and S. There is another approach that can be used in some cases, with additives directly into the pickling acid tanks. Hydronet D is the name of our product that can be added directly into Hydrochloric acid tanks at the typical concentrations and temperatures used by North American galvanizers. Acidic Degreasing in the pickle tank Without help, Hydrochloric and Sulfuric acids are not very effective at removing dirt. Hydrochloric acid in particular is poor at lifting greases, oils, chalk, and most other soils. Sulfuric is a little better, but more because it is heated AND attacks scale and rust by blowing off the top layers of rust IF it can penetrate the cracks in the scale. Generally, degreasing with an additive in the pickle tanks is not as effective as a stand-alone tank with SB Clean-Caustic or Hydronet Base or S; however, for

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