Tech Forum Salt Lake City October 2012 Fluxing.... Easy.... Right? Brian Anderson

The Chemistry of flux coating - Flux stability - Reactions from Impurities - Importance of Film thickness

/ Page 3 What do we control?  Density  Zinc Chloride (ZnCl 2 )  Ammonium Chloride (NH 4 Cl)  Iron  pH  Temperature What do we not consider?  Flux coating thickness

Flux solution - composition / Page 4 Zinc Chloride Ammonium Chloride FLUX chemicals Impurities Iron Water

/ Page 5 Cl Zn Cl H H H N Cl - Ammonium Chloride (NH 4 Cl) Zinc Chloride (ZnCl 2 ).. Ferric Chloride (FeCl 3 ) Cl Cl Fe Cl Cl Fe Cl Ferrous Chloride (FeCl 2 ) O H Water (H 2 O) H+H+

/ Page 6 H H H N Cl -.. H+H+ H H H N Cl H.. δ+δ+ δ-δ- Cl Zn Cl δ+δ+δ-δ-δ-δ- Ammonium Chloride Zinc Chloride

N Zinc Ammonium Chloride / Page 7 Cl Zn Cl H H H N Cl -.. H+H+ HHH Cl - H+H+ --- δ+δ+ δ+δ+ δ-δ- δ-δ- Zinc Chloride = 56% Ammonium Chloride= 44% ACN= 0.78 Molecular ratio= 2.0 : 1.0 (Double salt) Ammonium tetrachlorozincate

Reactions of Ammonium Chloride 4NH 4 Cl  4NH 3 +4HCl Ammonium Chloride Ammonia Hydrogen Chloride In molten zinc 4HCl + 2Zn  2ZnCl 2 +2H 2 Hydrogen Chloride Zinc Zinc Chloride Hydrogen 2ZnCl 2 + 2H 2 O  2ZnO + 4HCl Zinc Chloride Water Zinc Oxide Hydrogen Chloride (Ash) On molten zinc surface

.. N --- Zinc Ammonium Chloride - stabilization / Page 9 Cl Zn Cl H H H N Cl -.. H+H+ HHH Cl - H+H+ --- δ+δ+ δ+δ+ δ-δ- δ-δ- Cl Zn Cl

H + - O H + - O -.. H + H - O -.. H O H + Ionic solutions / Page 10..

Flux coating - ideal / Page 11 IRONIRONIRONIRONIRONIRONIRON.. +H4N+H4NCl Zn Cl --- Cl -.. NH H4N+H4NCl Zn Cl --- Cl -.. NH H4N+H4NCl Zn Cl --- Cl -.. NH H4N+H4NCl Zn Cl --- Cl -.. NH H4N+H4NCl Zn Cl --- Cl -.. NH 4 +

After HCl Pickling / Rinsing / Page 12 IRONIRONIRONIRONIRONIRONIRON O H O H O H Cl H O H O H O H O H Cl Fe Cl Fe Cl H O H O H O H Many impurities on the steel surface

After H 2 SO 4 (Sulphuric acid) Pickling / Rinsing / Page 13 IRONIRONIRONIRONIRONIRONIRON O H O H O H O H O H O H O H S O O OHHO O H S Fe++ O O O-O- O-O- Many impurities on the steel surface

Thin Flux coatings / Page 14 IRONIRONIRONIRONIRONIRONIRON.. +H4N+H4NCl Zn Cl --- Cl -.. NH H4N+H4NCl Zn Cl --- Cl -.. NH H4N+H4NCl Zn Cl --- Cl -.. NH 4 + O H O H Incomplete flux film formed Cl Fe Cl Fe Cl Cl Cl Fe Cl Ionic molecules compete for stable sites on the steel surface

/ Page 15 2H 2 O + Fe  Fe(OH) 2 + H 2 Ferric Chloride IronFerrous Hydroxide Hydrogen Steel surface Kettle Reactions of Water Fe(OH) 2 + 2Zn  2ZnO + Fe + H 2 Ferric Hydroxide ZincZinc Oxide Iron Hydrogen (Ash) 7Fe + 93Zn  Fe 7 Zn 93 Iron Zinc Dross Kettle

/ Page 16 2FeCl 3 +Fe  3FeCl 2 Ferric ChlorideIron Ferrous Chloride FeCl 2 + 2H 2 O   Fe(OH) 2 + 2HCl Ferrous ChlorideWater Ferrous Hydrogen Hydroxide Chloride FeCl 2 + 2H 2 O + 3Zn  2ZnO + ZnCl 2 + Fe + 2H 2 Ferrous Water Zinc Zinc Zinc Iron Hydrogen Chloride Oxide Chloride (Ash) (Ash) Steel surface Flux Kettle Ferric Chloride: Ferrous Chloride: Reactions of Iron Chloride

Flux film - Ideal / Page 17 IRONIRONIRONIRONIRONIRONIRON.. +H4N+H4NCl Zn Cl --- Cl -.. NH H4N+H4NCl Zn Cl --- Cl -.. NH H4N+H4NCl Zn Cl --- Cl -.. NH H4N+H4NCl Zn Cl --- Cl -.. NH H4N+H4NCl Zn Cl --- Cl -.. NH 4 +

Cl Flux film – Thicker film / Page 18 IRONIRONIRONIRONIRONIRONIRON.. +H4N+H4NCl Zn Cl --- Cl -.. NH H4N+H4NCl Zn Cl --- Cl -.. NH H4N+H4NCl Zn Cl --- Cl -.. NH 4 + Cl - Zn Cl --- Cl -.. NH NH 4 + Cl - Zn Cl --- Cl -.. NH NH 4 + Cl - Zn Cl --- Cl -.. NH NH 4 + Cl - Zn Cl --- Cl -.. NH NH 4 + Cl - Zn Cl --- Cl -.. NH NH 4 + Zn Cl Zn Cl O H O H O H O H O H O H Cl Fe Cl

Ideal Flux films - summary / Page 19 Zinc Chloride concentration greater than Ammonium Chloride Low iron (impurity) concentration - Form a complete flux film - Increase flux competing for sites on the steel surface Increase Flux concentration to: Minimum Ammonium Chloride concentration (reduced fumes)

Conclusions / Page 20 Reduces the impurity reactions with the steel surface So, Fluxing....Easy....Right?It is now! Improved Quality fluxing Faster drying of flux film to form a drier film Short immersion times -Iron Chloride -Water

Tech Forum Salt Lake City October 2012 Fluxing.... Easy.... Right? Brian Anderson