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Blog - Author: Robert Woods

Author: Robert Woods

Galvanizing 106

By Robert Woods
April 01, 2021 Category: Galvanizing

Galvanizing 106 As noted in the last commentary, tanks with either sodium hydroxide (aka caustic or an alkaline degreaser) or phosphoric or other acid (acid degreaser) are the two most common cleaning solutions for North American galvanizers. Well talk a bit about acid degreasing in this note. Acidic Degreasing Phosphoric-based As the name implies, acidic degreasing is done using chemicals that have a low pH, below pH of 7. The issue with acid-side cleaning is that strong acids like hydrochloric or sulfuric are poor at lifting soil from the surface of the incoming steel. To combat this, most stand-alone acid degreasers use a different acid, phosphoric acid, as the base for the cleaning. It is not great on its own, though, and so a number of components are added in a very complex balance to get the best cleaning results. Hydronet, the acidic degreaser from Zaclon, is such a balanced effective degreaser. Based on phosphoric acid, it has additives to lift soils, greases, oil, and convert

Galvanizing 105

By Robert Woods
April 01, 2021 Category: Galvanizing

Robert M. Woods SO how do we clean parts if we dont want to use (or only use) mechanical cleaning, or anything but spot-treat with solvent cleaners? Using dip tanks with either sodium hydroxide (aka caustic or an alkaline degreaser) or phosphoric or other acid (acid degreaser) are the two most common cleaning solutions for North American galvanizers. Well talk a bit about alkaline degreasing here, and acid degreasing next time. Alkaline/Caustic Degreasing Caustic is used interchangeably with sodium hydroxide, the primary component in these types of cleaners. The high pH (highly alkaline) solution can react with many oils and greases, particularly natural oils, and since it typically is heated to 135 F or more, the bath is more generally active. Caustic is typically kept at about 10% concentration, by adding fresh caustic solution (50%) or the pellet-form solid. The strong alkaline nature of this bath does make it more hazardous chemically than most of the other tanks in a galvanizer,

Galvanizing 103

By Robert Woods
April 01, 2021 Category: Galvanizing

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?

Galvanizing 104

By Robert Woods
April 01, 2021 Category: Galvanizing

Robert M. Woods Mechanical cleaning and elbow grease can take care of a number of the soils that end up on the steel as it is processed and transported to the galvanizer, but what about hidden areas, places where rivets or open welds, bolts, and inside of hollow-ware? To get these cleaned up, a chemical dip of some sort is the best approach, whether in the form of a vapor degreasing, waterless solvent cleaning, or full-scale acid or alkaline degreasing in a water solution. Vapor degreasing is effective, but typically for smaller parts---it simply takes a solvent such as acetone, heats it in a carefully closed system until it evaporates, then lets that vapor hit the cooler part and condense. The warm solvent can give excellent cleaning, and properly selected will leave no residue. In some cases the solvent can also be recycled. Downside, though, is keeping the vapors in the cabinet can be quite challenging; plus air permits and the like may be involved. Similar issues appear with

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