Dip coating is a process used to prepare porous ceramic membranes by immersing a substrate into a precursor solution, removing it, and allowing the coating to dry. It is an old commercially applied coating technique dating back to a 1939 patent. Key steps to forming defect-free membranes include using a homogeneous support, cleaning the substrate, sufficiently deaerating the solution, avoiding thick coatings, and keeping the environment particle-free. The dip coating process involves three stages: immersion for wetting, deposition and drainage as the substrate is withdrawn, and evaporation of the solvent to form the dried coating layer. Withdrawal speed and other forces determine the thickness of the coated layer.

1. Dip Coating
Presented By
Engr. Mukhtiar Ahmed
Supervised By
Dr. Saeed Gul
Chemical Engineering Department
University of Engineering & Technology Peshawar

2. Dip Coating
 Introduction
 Background
 Applications
 Methods

3. Dip Coating
Introduction
“Dip Coating refers to the immersing of a substrate
into a tank containing precursor solution, removing
the piece from the tank, and allowing it to drain.”
It is widely used for the preparation of porous
ceramic membranes.[1]

4. Dip Coating
Background
 Oldest commercially applied coating process
 First patent based on this process was issued to
Jenar Glaswork Schott and Gen in 1939
 Before dip coating porous substrate has to be
polished with a layer of smaller particles

5. Dip Coating
Steps to form defect-free membranes[2]:
 A homogenous support
 Substrate cleaning and filtration
 Sufficient de-aeration of sol/suspension
 Not too thick coating which results in drying
shrinkage and tensile stress
 Avoid dust and other foreign particulates in air or
coating fluids

6. Dip Coating
Process
The process may be separated into three important technical
stages[3]:

Immersion & dwell time: The substrate is immersed into the
precursor solution at a constant speed followed by a certain
dwell time in order to leave sufficient interaction time of the
substrate with the coating solution for complete wetting.

Deposition & Drainage: By pulling the substrate upward at a
constant speed a thin layer of precursor solution is entrained, i.e.
film deposition. Excess liquid will drain from the surface.

7. Dip Coating
 Evaporation: The solvent evaporates from the
fluid, forming the as-deposited thin film, which can
be promoted by heated drying. Subsequently the
coating may be subjected to further heat
treatment in order to burn out residual organics
and induce crystallization of the functional oxides.

8. Dip Coating
Substrate is usually withdrawn vertically from
solution reservoir at constant speed
Withdrawal speed ranges from 1-10mm/s
Competition among various forces decide the
thickness of coating
Dip-coating is dependent on angle of
withdrawal

9. Dip Coating

10. Dip Coating
References:
[1] Geffcken W, Berger E (1939) Verfahren zur Anderung des Reflexionsvermogen
Gla¨ser. Deutsches Reichspatent, assigned to Jenaer Glaswerk Schott & Gen.,
Jena 736 41
[2] Scriven LE (1988) Physics and application of dip-coating and spin-coating In:
Brinker CJ Clark DE, Ulrich DR (eds) Better ceramics through chemistry III,
vol 121, Materials Research
[3] Grosso D (2011) How to exploit the full potential of the dip-coating process to
better control film formation. J Mater Chem 21:17033–17038