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-----Galvanizing Without Rinsing
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Q. I am seeking your expert guidance regarding the most suitable degreasing process for a galvanizing application.
Currently, I am evaluating the following four degreasing methods commonly used prior to galvanizing:
1. Hot alkaline degreasing
2. Acid degreasing
3. Solvent degreasing (petroleum-based or Trichloroethylene/TCE)
4. Biological degreasing
From a technical and operational standpoint, I would appreciate your professional opinion on the following points:
• Which degreasing process is considered the most effective and reliable for surface preparation before galvanizing, considering oil/grease removal efficiency and coating quality?
• What are the key advantages and limitations of each process in terms of surface cleanliness, environmental impact, safety, operating cost, and compatibility with galvanizing?
• Is there any degreasing process that can eliminate or minimize the rinsing stage while still ensuring acceptable surface quality for galvanizing?
• If rinsing removal is feasible, what precautions or process controls are critical to avoid contamination or defects during galvanizing?
Your guidance will be extremely valuable in helping us select a technically sound and sustainable degreasing solution.
new developer in arvind corrotech ltd. - Nadiad- gujarat - India
January 8, 2026
A. There are two major systems of degreasing using Hot Dip Galvanizing. Both are a dip process in the pretreatment area of the plant. These are acid degreasing and alkali. Solvent and biological degreasing are not used being either dangerous (fire risk) or ineffective against the variety of oils, greases and paints that are encountered.
Acid degreaser:
• Advantages are that no rinse is required between degreasing and acid cleaning (typically HCl, but in some countries the more expensive and energy consuming sulfuric acid pickling). So now rinse required after acid degreasing, no major heating of the liquid required (except arctic countries).
• Disadvantages: less effective that alkali, but the difference is only noticed in severe oiling cases. Residue falls to tank bottom as a sandy glutinous deposit that needs cleaning out perhaps annually. Will not remove paint. Tanks must be acid proof. Mostly based on phosphoric acid with many additives.
Alkali degreaser:
• Requires heating, typically these degreasers run at 50-70 °C, ineffective below 45 °C. That means more evaporative loss to be made up with water. Highly effective degreaser. No special tank, plain uncoated mild steel is OK. Most of these are based on NaOH with surfactants, sometimes chelates. Much less effective without additives, yet some plants run NaOH only, and it does not work near as well. Steel must be rinsed afterwards otherwise the alkali neutralises the acid in the subsequent tanks, forming NaCl which eventually gets to the flux tank contaminating it.
Alkali degreaser costs significantly more to run (total running cost, not just chemical cost). It is recommended in the case of very oily work, such as lubricant removal from roll formed sheetmetal parts, drilling and cutting lubricant removal, or, mostly in Australia where fabricators can only buy some steel pre-painted with blue paint.
Acid degreaser is lower cost and easier to manage, save energy, saves a tank (rinse). There is no general rule, each situation needs evaluation to decide between the two.
Geoff Crowley, galvanizing consultant
Crithwood Ltd.
Bathgate, Scotland, UK
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