Corrosion Detection through SEM / EDX analysis

Glen May

Process fluids for the T&P industry

» Water soluble fluids are used in various

operations in the pipe producing process

» What is the primary need

for a process fluid for a

T&P MW product? – Corrosion Protection

– Lubrication

– Cooling

– Chip removal

Process fluids used in T&P

Pipe corrosion

» Totally unacceptable – Effect the pipe integrity

– Negative effect on aesthetics

– Delayed detection – economically damaging

• Corrosion problems are not noticed until

after the bundle has been opened

• Many tons of pipe have been produced

before the problem has been detected

Understanding corrosion types

» Corrosion is a chemical reaction and is

dependent on many factors: – pH, and concentration of the process fluids

– Chloride content of the water and subsequently the fluid

– Oxygen

– Humidity

» Several different forms– Passive

– Homogeneous

– Galvanic

– Crevice

– Pitting

Importance to understand corrosion

» Find the source – Almost all T&P corrosion problems are related to Iron

hydroxide/ oxide with bound in water – commonly

know as rust

» Better understand for the future to help

prevent corrosion– Process

– Environment

– Fluids

» Help develop metal working fluids

1. Electrons are fired into the machine.

2. Vacuum chamber

3. Anode accelerates the beam .

4. An electromagnetic coil focuses the beam

5. Another coil steers the electron beam.

6. The beam systematically scans across the object

being viewed.

7. Electrons from the beam hit the surface of the

object and bounce off it.

8. A detector registers these scattered electrons and

turns them into an image.

9. A hugely magnified image of the object is displayed

on a monitor

SEM basics

SEM visual

» Typical surface corrosion – surface is

etched due to trapped water.

» The holes are darker due to

contamination of Oil and Carbon

» This surface has minimal etching but

shows some deposits indication that the

corrosion was caused by open

air/humidity

» Left in Air only – low humidity

» High levels of Carbon

EDX basics

» Uses the X –ray radiation generated during the E

beam hitting the specimen surface to create an

Atomic map of the surface

SEM / EDX raw data example

» Here we see higher

levels of Cl and Na in the

stained area

» This trend is also seen

with O and Fe

» The source of the NaCl

was contamination in the

hydro-testing fluid from

the hot rolling process

Field Corrosion example

» Staining / Bluish spots

seen on HR Square Tube

SEM image of the staining

» SEM analysis shows an unusual scale

» Not typical of normal HR scale which

characteristically contains a lot of

Oxygen

EDX results

» Some presence of N – which could

come from the mill lubricant

» High levels of O are expected in the

corrosion scale

» Random distribution of Ca indicates

that it is not linked to the scale

problem

» High levels of Cu are clearly seen.

» Cu is a known catalyst for Galv

corrosion

Problem conclusion

» The source of the Cu was traced

to the soluble mill lubricant

» High levels of Cu are unusual in

metal working fluids unless they

are machining or working high

Cu alloys

» It was found that the steel was

made from Cu contaminated

scrap

» The Cu subsequently leached in

to the mill fluid and increased in

concentration over time

QUESTIONS?

Glen May

+49 172 452 6572

Mayg@quakerchem.com