Crater Contamination Training (June 2007) - PPG Industries Contamination... · Craters are a...

Confidential 1PPG Industries

Crater ContaminationCrater Contamination--

The Path TowardsThe Path TowardsZero CratersZero Craters

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• Purpose• Seriousness Of Craters• What Is A Crater?• When Do Craters Occur?• What Causes PDMS Caters?• What Is Silicone?• Crater Stories• Crater Prevention• Crater Risk Principles• Management Of Change


1. Craters are a serious defect in paint quality especially in the Automotive industry.

2. PPG aims to supply zero crater products through strict quality control. This includes raw materials, intermediates and packaging supplied to PPG.

3. PPG must be assured that all supplied products are free from crater contamination.

4. This presentation shows how contamination in materials and processes may be prevented.

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When significant craters appear in paint or clear coat on an automotive production line the following issues may ensue:– Stop production – RISK ~ $10,000 / minute cost– Additional labour for repairs and rework - $$?– Car bodies may be scrapped ~ $20,000 each– Coating system may be dumped – waste paint

disposal ~ $2,000 + per ton.– Loss of customer confidence in supplier– Loss of business as supplier

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Craters are a dish shape deformation in a paint surface that may, in extreme cases, penetrate to the layer below. They are typically 1 – 4 mm in diameter.

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Craters can occur:

– While the paint film is a liquid.

– During paint application.

– During the flash off of the applied paint film

before baking.

– During the baking of the paint film while still in

a liquid state.

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Craters can be caused by contamination of the paint by a particle (solid or liquid) of a low surface tension material that is insoluble or marginally soluble in the paint coating.

Paint materials typically have surface tensions of between 30 and 50 dynes per cm.

Typical contaminants are oils, greases, O-Rings, plastic and rubber gaskets with ~ 25 dynes per cm surface tension.

The most aggressive contaminants are Silicones, Fluoro and Teflon sealant compounds (liquid or solid) with surface tensions ~20 dynes per cm.

It only takes 2 - 3 dynes /cm surface tension difference to drive crater formation.

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• When Silica is reacted with Alkyl Chloride and water you can get long chain compounds with the following structure.

HO-[Si (R or OH)2]n-OH• If the organic groups R are large and form a high

proportion of the side groups the compound has an oily character and can be used in coatings without crater risk (ex: Silicone based additives)

• When the organic side groups are Methyl, the compound is PDMS, Poly Di Methyl Siloxane, and this is a classic CRATER causing compound.

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PDMS, Silicone has numerous uses. It can be anything from a thin oil to a semi solid grease depending on the chain length.

It can be used as a lubricant, cleaner, dirt repellent, storage protective agent, water repellent, etc. It is found in everything from hair spray to lubricant in valves and pumps.

Even if analysis shows the contaminant to be PDMS you are far from identifying the root cause because there are so many potential sources.

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Recycled Drums – Solvent distributor used recycled drums as intermediate storage before

filling for delivery to PPG customer. Solvent was used to reduce OEM customer paint

system causing craters.

Drum Lining Changes – Supplier of new drum liner makes formula change without

notifying drum manufacturer or PPG. PPG paint was filling into these new drums and the

new liner chemicals leach out into paint causing OEM customer paint craters.

New Tote Valves – Tote Cleaner changed to new replacement valves which were

contaminated with silicone without notifying us. PPG paint was filling into these cleaned

and repaired totes silicone leach into paint causing OEM customer paint craters.

New Filter and Recycle Process – Speciality solvent supplier added an inline filter with a

recycling line and five new valves contaminated with silicone without notifying us. PPG

adds this solvent to paint at a very low percentage. This contaminated paint causes

OEM customer paint craters.

Tanker Trailer Cleaning – Tanker cleaner failed to clean and flush out belly tube

contaminating PPG intermediate resins.

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Crater Education

Cleaning

CRATER PREVENTION

Crater prevention requires a broad approachin order to manage the diverse contaminant sources.

Man

ufac

ture

Pro

cess

5S ProcessAvoiding Introducing

Contaminants

Raw materials and intermediates

Facilities, tanks, pumps, valves,

bulk railcars and tanker trucks

Personal items(hand cream, hair spray deodorants and cosmetics)

Use Approved Materials

Crater Prevention Strict control of Silicone usage

Preventingenvironmental contamination

Education on crater risksfor Employees and suppliers

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Environment ManProcess

Coating materialMachine

Craters in Clearcoat

Contamination of body through people on line

Improper Wiping of primer

Improper application resulting in overspray

Contaminated Paint

Contaminated Thinner

Contaminated Wiping Solvent

Formulation change

Faulty equipment cleaning

Contaminated valves

Welding operation in Paint Shop

Contaminated Barrel

Contamination during paint preparation

Booth Environment

Booth not under positive pressure resulting in overspray

Airline Contaminated by oil,water

Contamination in the mixer

RM variation at plant

Blending of new batch with existing line paint

Silicone GasketsSilicone RubberTeflon and Viton

Pump Oil

Chain and Gear Lubricants

WD-40 Type Lubricants

Cutting OilsTool and Machine

Lubrucants

Drum Machine OilsLubricants in Drums

Pail Manufacture

Contamination in Stationary, Transfer

and Transport Containers

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• Valves and Pumps and Filters– Ensure all parts are supplied silicone free.– Ensure parts are disassembled and cleaned before use

especially if “Silicone Free” status can not be assured.– Ensure replacement parts such as O-rings or gland

seals are “Silicone Free”.– Ensure filter manufactures do not sewing using Silicone

lubricated needles.

• Operator’s Clothing – Ensure garment manufactures do not use Silicone

lubricated needles for sewing.– Ensure garment cleaning process does not use or

contaminate clothing with Silicone.

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We cannot do 100% inspection or testing. We require assured quality.

We need to prevent contaminants being introduced into the process.

We need to establish through communication and auditing a

better informed Supplier network.

When craters occur we need to be able to follow root cause analysis.

The entire manufacture and supply process must be assured. We need notification of changes in process.

Maintaining an approved materials list and a crater cause list should help us

avoid using risky production materials.

We need to be able to foresee contamination risks to prevent defects.

Root cause must be tracked through manufacturing, delivery and usage.

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PPG notification of Supplier manufacturing

process changes is very important.

We ask all suppliers to use the PPG formal

“Management of Change” process.

The purpose is to avoid problems before they

impact the PPG supply quality.

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Crater Contamination Training (June 2007) - PPG Industries Contamination... · Craters are a...

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