Overview
Various cleaning agents are used in metal degreasing processes. In recent years, hydrocarbon cleaning agents have become increasingly common as alternatives to chlorinated organic solvents. Hydrocarbon solvents are broadly divided into normal paraffin (n-paraffin) and iso-paraffin. This article introduces their characteristics based on differences in molecular structure.
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1. Types of Degreasing Agents
Purpose of Degreasing
Metal products are exposed to various processing oils and release agents during manufacturing, leaving oils and contaminants on metal surfaces. These must be removed through cleaning processes as they can cause defects in subsequent coating or plating processes. It's essential to use cleaning agents appropriate for the specific purpose.
Types and Characteristics of Degreasing Agents
While there are various types of cleaning agents used in degreasing processes, here are the most commonly used ones:
1-1 Aqueous Cleaning Agents
Aqueous cleaning agents use water as a solvent and contain surfactants, inorganic and organic additives as main components.
They are further classified into:
- Acidic cleaners: Contain inorganic and organic acids, effective against rust
- Neutral cleaners: Contain surfactants with neutral, slightly acidic, or slightly alkaline properties
- Alkaline cleaners: Contain sodium hydroxide or sodium bicarbonate, remove contaminants through neutralization and saponification
The main disadvantage is the requirement for wastewater treatment facilities.
1-2 Chlorinated Organic Solvent Cleaners
These cleaners contain organic compounds with chlorine atoms bonded to carbon chains. Benefits include high oil solubility and distillation recyclability. Being non-flammable, they enable vapor cleaning for quick and consistent results. However, due to high toxicity and environmental impact, strict regulations have led to their replacement with hydrocarbon cleaners.
1-3 Hydrocarbon Solvents
Most metal degreasing hydrocarbon solvents are either normal paraffin or iso-paraffin based. Their advantages include low metal corrosivity and low toxicity, making them easier to handle. The ability to recycle through distillation offers cost benefits, making them popular in current degreasing processes.
2. Normal Paraffin and Iso-paraffin
2-1 What is Paraffin?
Paraffin refers to alkanes (CnH2n+2) with 20 or more carbon atoms. It's a translucent or white solid produced through crude oil distillation, insoluble in water and chemically stable. There are mainly two types: normal paraffin and iso-paraffin.
2-2 Differences in Molecular Structure
The key difference lies in their molecular structure. Normal paraffin has a linear molecular chain, while iso-paraffin has branched molecular chains.
2-3 Differences Between Normal Paraffin and Iso-paraffin
The main difference is cost. While iso-paraffin has a slight odor, cleaning performance (cleaning ability, drying properties, regeneration efficiency) is nearly equivalent. However, iso-paraffin is typically less expensive due to having more manufacturers.
