Contents
Partially compliant

ASTM G205 guide for determining emulsion properties, wetting behavior and corrosion inhibitory properties of crude oils

ASTM G205 judges whether a crude oil lets water corrode carbon steel, from emulsion type, steel wettability and water phase corrosivity. With the optional cuvette, the Dropometer reads the oil, water and steel contact angle G205 names for wettability, with ±0.35° accuracy. The emulsion inversion point, spreading and corrosion rate parts need conductivity and corrosion test equipment.

What brings you here?

Who this is for
Production, pipeline and storage operators, corrosion labs and corrosion inhibitor suppliers who rank crude oils by corrosion risk.
Compliance tier
Partially compliant: with the optional cuvette, the Dropometer reads the oil and water contact angle on steel. It does not run the emulsion, spreading or corrosion rate parts.
Measurement
Oil and water contact angle on steel, captive drop under brine with the optional cuvette, 10° to 175° range, ±0.35° accuracy (Dropometer datasheet).
Setup
About 2 minutes for the base unit. Battery powered, 1 kg, runs on the lab bench.
Last updated
October 20, 2026
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Free one page checklist for the ASTM G205 contact angle part: what to prepare, the settings to lock, the drop geometry and what to record. Made for corrosion and flow assurance labs.

Talk to an expert

Book a 15 minute demo on your crude and steel

Tell us your crude, brine and steel grade. We will show the captive drop measurement live and tell you plainly which parts of ASTM G205 the Dropometer covers and which it does not.

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View the official standard
Gurdeep-Saini-Photo
Written by
Gurdeep Singh Saini
Holds a BASc in Mechanical Engineering from Ryerson University (now Toronto Metropolitan University) and an MASc from York University. He develops the automatic edge and baseline detection behind the Dropometer's analysis.
COO at Droplet Lab
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Droplet-Lab logo
Technical Review by
Droplet Lab Team
Droplet Lab builds precision instruments and software for surface science measurement, specialising in contact angle analysis and surface tension characterisation. Used by researchers across materials science, pharmaceuticals, coatings, and advanced manufacturing, Droplet Lab's Dropometer has contributed to studies published in peer-reviewed journals including Advanced Functional Materials (Impact Factor 19). The team combines instrument engineering with deep domain knowledge in wettability science with a focus on practical accuracy.
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Verified against ASTM G205
Gurdeep-Saini-Photo
Written By

Gurdeep Singh Saini

COO at Droplet Lab

Holds a BASc in Mechanical Engineering from Ryerson University (now Toronto Metropolitan University) and an MASc from York University. He develops the automatic edge and baseline detection behind the Dropometer's analysis.

Droplet-Lab logo
Reviewed By

Droplet Lab Team

Droplet Lab builds precision instruments and software for surface science measurement, specialising in contact angle analysis and surface tension characterisation. Used by researchers across materials science, pharmaceuticals, coatings, and advanced manufacturing, Droplet Lab's Dropometer has contributed to studies published in peer-reviewed journals including Advanced Functional Materials (Impact Factor 19). The team combines instrument engineering with deep domain knowledge in wettability science with a focus on practical accuracy.

Featured Studies & Publications

Research Paper Contact angle measurement with a smartphone
Research Paper Surface tension measurement with a smartphone using a pendant drop

Evidence box: ASTM G205 and the Dropometer

Standard

ASTM G205-26, Standard Guide for Determining Emulsion Properties, Wetting Behavior, and Corrosion-Inhibitory Properties of Crude Oils, from ASTM International Subcommittee G01.05. Earlier editions include G205-16 and G205-23. The first edition, G205-10, was titled Standard Guide for Determining Corrosivity of Crude Oils.

Compliance tier

Partially compliant. With the optional cuvette, the Dropometer reads the contact angle where oil and water meet on steel, one of the two wettability approaches G205 names. The emulsion inversion point and spreading approaches use conductivity or resistance, and the water phase part uses corrosion rate tests. The Dropometer runs none of these.

Instrument performance

Contact angle range 10° to 175°, accuracy ±0.35°, display resolution 0.01°, from the Dropometer product specification. With the optional cuvette, the Dropometer also runs captive bubbles, captive drops under a submerged sample, and interfacial tension by pendant drop of one liquid in another.

Peer reviewed method

The drop shape method is validated against a KRUSS DSA100E in two peer reviewed papers. See our validation publications.

Customer evidence

We have no published client paper or case study on crude oil wettability of steel yet. For a related workflow, see wettability alteration screening.

What it does not tell you

A wettability reading on its own does not give a corrosion rate. G205 weighs emulsion type, wettability and water phase corrosivity together. Pair the angle with your emulsion and corrosion tests.

Executive summary: ASTM G205 and the corrosivity of crude oils

What this guide covers, who uses it and how the Dropometer fits

ASTM G205 is an ASTM guide for judging whether a crude oil will let water corrode carbon steel, from a combination of three properties: emulsion type, steel wettability and the corrosivity of the water phase. Production, pipeline and storage operators, corrosion labs and chemical suppliers use it to rank crudes and plan inhibition for crude oil handling and transport. The water phase can cause corrosion only where it reaches the steel, so the question is whether a crude oil that contains water keeps that water in an emulsion and the steel oil wet. The Dropometer is partially compliant: with the optional cuvette it reads the oil, water and steel contact angle that G205 names for wettability, with ±0.35° accuracy. It does not run the emulsion inversion point, spreading or corrosion rate parts.

G205 lists two ways to judge steel wettability. The contact angle approach observes the angle where oil and water meet on the steel. The spreading approach measures electrical resistance between isolated steel pins. G205 describes approaches rather than detailed procedures, so each lab sets the geometry, liquids and drop volume in its own method. Many published studies place an oil drop under a steel coupon held in brine and read the angle through the water. G205 also points to the water and sediment content of crude oil, measured by separate ASTM test methods. For good bench practice, see reproducible contact angle measurement.

The Dropometer contact angle and surface energy kit reads this angle on battery power at the bench. To screen chemicals that shift wetting, see wettability alteration screening for surfactants and chemicals. For background, read the oil and gas guide and the contact angle measurement guide.

Further reading: capillary number, water contact angle reference values for common surfaces and choosing a contact angle goniometer for industrial QA.

How the Dropometer fits the wetting behavior part of G205

The ASTM G205 contact angle part, step by step, in our own words

From steel coupon to a recorded oil and water angle

These steps outline one common way to run the contact angle part of G205 with the Dropometer and the optional cuvette. They do not replace the guide. Buy the current edition and set the liquids, drop volume and timing in your own written method.

±0.35°

Contact angle accuracy

From the Dropometer product specification. Display resolution is 0.01°.

10° to 175°

Contact angle range

Covers most water wet to strongly oil wet readings. A drop that rolls off reads above range.

Cuvette

Optional accessory

Holds the brine and the submerged coupon for the captive oil drop. The same optional cuvette runs oil and brine interfacial tension.

1

Prepare the steel coupons

Cut flat coupons from the steel grade in your line. Polish, clean and dry them the same way every time, and handle them by the edges. If your method ages coupons in crude first, record the ageing time and rinse step.

2

Prepare the brine and the oil

Make a brine that matches your produced water, and deaerate it if your method calls for that. Most crudes are opaque, so put the crude in the drop, not in the bulk phase. If you need a water drop under oil, use a clear model oil as the bulk phase.

3

Set up the Dropometer and cuvette

Level the base plate, mount the phone and LED, and fill the optional cuvette with brine. Hold the coupon face down in the brine. Custom holders are available on request. Let the coupon soak for the time your method sets.

4

Place the oil drop under the coupon

Release the oil drop below the submerged coupon in the optional cuvette, so it rises and settles on the steel. A captive drop under a submerged sample is a supported Dropometer setup. Use the drop volume your method sets and keep it the same for every drop.

5

Capture and read the angle

Capture the drop at the reading time your method sets. Automatic edge and baseline detection reads the left and right angles, so two operators get the same reading from the same image. Report the angle through the water phase, as most crude oil studies do.

6

Repeat, record and combine

Repeat on fresh coupons or fresh areas. Record the mean, spread, crude, brine, steel, finish and room temperature. Then read the angle together with your emulsion and corrosion results, as G205 intends.

7

Watch the full measurement

This video shows a complete Dropometer contact angle measurement, from setup to result. It covers the steps above in one run.

Dropometer contact angle measurement, start to finish.

Validated measurement approach

Independent benchmarking and publication-based validation references.

Peer reviewed method

The Dropometer drop shape method is validated against a KRUSS DSA100E in two peer reviewed papers, one in Review of Scientific Instruments and one in Colloids and Surfaces A. Published contact angle accuracy is ±0.35°.

Read the validation papers

Customer evidence

We have no published client paper or case study on crude oil wettability of steel yet. The wettability alteration use case shows how oil and water contact angles screen chemicals that shift wetting.

Read the use case

Set limits from your own crude oils and steel

ASTM G205 · steel wettability · crude oil corrosivity

The public ASTM summary of G205 classes steel as oil wet (hydrophobic, not prone to corrosion) or water wet (hydrophilic, prone to corrosion), but gives no angle limit (source: ASTM G205-26 summary).

Published studies use different cut points. One study of heavy crude on pipeline steel, angle read through the water, called below 70° water wet, 70 to 110° neutral and above 110° oil wet (source: dos Santos et al., COBEM 2003). A later crude oil study used 90° as the neutral point (source: Richter et al., 2014).

So set your own action limit from a correlation study. Measure crudes with a known field record, then compare the angles with your spreading and corrosion rate results. Repeat the study when you change steel grade, surface finish, brine or test liquid.

Example output

Example data for illustration only. These are not measured results. Your own crude, brine, steel and limits decide the numbers.

Example: four crude oils, oil drop under carbon steel in brine, angle through the water

Crude oil Drops (n) Mean angle through water (°) Std dev (°) Example band Decision
Crude A5152.43.1Oil wetAbove limit: confirm with corrosion test
Crude B5118.64.2Oil wetAbove limit: confirm with corrosion test
Crude C594.33.8NeutralNear limit: run the spreading test
Crude D548.72.9Water wetBelow limit: test water phase corrosivity

How to read this table

Each row is the mean of five drops on fresh coupons. The band column uses the example bands from one published study. The decision column uses an example action limit of 90°, set from a correlation study with corrosion rate tests.

Example output chart

The same example data as the table, plotted against example wetting bands from one published study and an example action limit.

Bar chart of example oil and water contact angles on carbon steel for four crude oils, with example wetting bands at 70 and 110 degrees and a 90 degree action limit

Example data, not measured results.

Business impact

What changes when steel wettability is a measured angle

Metric Before Dropometer With Dropometer Results
How wettability is judged Inferred from field history or emulsion behaviour Oil and water contact angle on your steel, read from the drop image No published benchmark
Result format Oil wet or water wet, by judgement An angle per drop, 0.01° display, ±0.35° accuracy Dropometer product specification
Record Lab notebook entry Drop image and angle saved per measurement No published benchmark
Emulsion, spreading and corrosion rate Conductivity, resistance and corrosion test rigs Still need those rigs ASTM G205 significance and use

See the measurement on your own crude

Bring a crude with a good field record and one with a corrosion history. We will measure both live under brine on your steel.

Book a 15 minute demo Request a quote
ROI estimate

Estimate the cost of the corrosion failures this screen can help catch

Enter your own numbers. The defaults are examples, not Droplet Lab results.

Quality cost snapshot

Estimate what wetting related failures cost you.

Example only. Use what you see in a trial on your own samples.
Your own figure.
Your own estimate.

Result

~0
Estimated annual cost today
~0
Estimated annual cost avoided
~0
Payback period

Annual exposure combines audit/CAPA cost, customer rejections, and recall probability; avoided exposure applies the risk reduction percentage.

Method settings for the G205 contact angle

Lock these before you compare crudes, labs or campaigns

Parameter Recommended Setting Technical Rationale
Steel The grade and finish in your line, prepared the same way each time Finish and corrosion product layers change wetting, so the coupon must match your question.
Bulk phase Brine in the optional cuvette Most crudes are opaque. A clear bulk phase lets the camera see the drop outline.
Drop phase and geometry Crude oil drop under the submerged coupon, captive drop in the optional cuvette The oil rises onto the steel. A water drop on top under clear model oil is the other common layout.
Angle convention Through the water phase, stated in the report Most crude oil studies report it this way. Higher angles then mean more oil wet.
Drop volume As your method sets, fixed for every drop G205 gives no drop volume. The automatic dropper doses down to 0.05 µL.
Soak and reading time As your method sets, fixed for every drop Crude components adsorb on steel over time, so the angle can drift.
Fit model Young-Laplace or polynomial, the same for every run Both models are in the Dropometer software. Do not mix them within one study.
Environment Room temperature, recorded G205 covers water up to about 100 °C. The Dropometer has no temperature control and runs at 10 to 45 °C.

Which part of ASTM G205 do you need?

Pick the method by the question you need answered

Start: What do you need to know about your crude and the steel?

Steel wettability as an angle

Signals:

You want to know whether a crude leaves steel oil wet or water wet, as a number per crude.

Rule-out:

Use the G205 contact angle approach, this page. The Dropometer is partially compliant and runs this part as a captive oil drop under the submerged coupon, with the optional cuvette.

Emulsion type and inversion point

Signals:

You need the water cut at which a water in oil emulsion turns into oil in water.

Rule-out:

Use the G205 emulsion inversion point approach, which tracks the conductivity of the emulsion. The Dropometer does not run it.

Wettability from electrical resistance

Signals:

You want a wetting reading from oil and water mixtures across steel pins.

Rule-out:

Use the G205 spreading approach with a multi electrode array. The contact angle complements it.

Corrosivity of the water phase

Signals:

You need a corrosion rate, or whether the crude inhibits corrosion.

Rule-out:

Use the corrosion tests G205 points to, such as ASTM G170, G184, G185 and G202. The Dropometer does not measure corrosion rate.

Decision tree at a glance

Start from the question you need answered. The blue box is the part of G205 the Dropometer runs, with the optional cuvette.

Decision tree for choosing between the ASTM G205 contact angle approach on the Dropometer, the emulsion inversion point test, the spreading test and corrosion rate tests

Which part of ASTM G205 do you need?

Interpreting wetting behavior and corrosion risk

What the angle tells you, and what it does not

Higher angle through water, more oil wet: When oil holds the steel surface, water cannot reach it, and G205 treats oil wet steel as less prone to corrosion.
Neutral angles need a second test: Angles near 90° sit between the published bands. Confirm with the spreading test or a corrosion test.
Wetting can change with time: Crude components adsorb on steel. Record soak time, and compare crudes only at the same soak and reading time.
Angle is one of three inputs: G205 weighs emulsion type, wettability and water phase corrosivity together. One oil wet reading does not clear a crude.
Expert perspective

Why the oil and water angle on steel tracks corrosion risk

Place a drop and just read it and you get an apparent angle: a value somewhere between advancing and receding that isn't much use. Zisman settled that in the fifties.

Dr. Alidad Amirfazli

Department of Mechanical Engineering, York University, Co-founder and Scientific Advisor, Droplet Lab

Pitfalls and limits for crude oils on steel

Honest limits of the method and of the Dropometer

Opaque crude in the bulk phase hides the drop. Put the crude in the drop, or use a clear model oil on crude aged steel.
The Dropometer has no temperature control and does not test under pressure. Results are at room temperature, not line conditions.
Strongly oil wet steel can push the angle past 175°, the top of the Dropometer range. Report those drops as above range.
G205 judges wetting from the angle, not from interfacial tension. If your study also needs oil and brine interfacial tension, the Dropometer measures it by pendant drop with the optional cuvette. Check it on a known liquid pair first.
Oil and water angles, captive drops and interfacial tension all need the optional cuvette, so order it with the base unit.
The camera runs at 10 frames per second. That suits a reading at a fixed time, not millisecond spreading studies.
FAQ

Frequently asked questions

What does ASTM G205 cover?

ASTM G205 is a guide to laboratory methodologies for judging the corrosivity of crude oil where water is liquid, typically up to 100 °C, as in oil and gas production, storage and pipelines. It looks at three properties: emulsion type, steel wettability and the corrosivity of the water phase. It is not meant for the higher temperatures of refining, typically above 300 °C.

Which parts of ASTM G205 use a contact angle?

Only the wettability part. G205 names two wettability approaches: the contact angle where oil and water meet on steel, and a spreading approach that measures resistance between steel pins. The emulsion and water phase parts use conductivity and corrosion rate tests.

Can the Dropometer run ASTM G205?

In part. With the optional cuvette, the Dropometer reads the oil and water contact angle on steel with ±0.35° accuracy. It does not measure the emulsion inversion point, spreading resistance or corrosion rate, so you need those rigs for the rest of G205.

Do I need the optional cuvette?

Yes. G205 looks at oil and water on steel at the same time, so the coupon must sit in a liquid. The optional cuvette holds the brine and the submerged coupon, and the oil drop is released under it as a captive drop, a supported Dropometer setup. The same optional cuvette runs captive bubbles and oil and brine interfacial tension.

How do I measure the angle when crude oil is opaque?

Put the crude in the drop and the clear brine in the cuvette, then read the drop outline through the water. If your method needs a water drop under oil, age the steel in crude and use a clear model oil as the bulk phase, as several published studies do.

What angle means oil wet in ASTM G205?

The public ASTM summary gives no angle limit. Published studies use different cut points, such as below 70° water wet and above 110° oil wet, read through the water. Set your own limit from crudes with a known field record. See dos Santos et al., 2003.

Does the Dropometer measure oil and water interfacial tension?

Yes, with the optional cuvette. The Dropometer measures oil and brine interfacial tension by pendant drop of one liquid in the other. G205 judges wetting from the contact angle and spreading approaches, so interfacial tension is an extra, useful when you study how a chemical changes oil and water behaviour. Check the setup on a known liquid pair first.

Legal note

This page summarises ASTM G205 in our own words and does not reproduce the guide. Buy the current edition from ASTM before you write a procedure. The Dropometer is partially compliant: it covers the contact angle part only, with the optional cuvette. Droplet Lab does not certify compliance. Your own method validation does.

View the official standard Book a 15 minute demo

How this page was created

Sources, review and tools

Transparency 4 checklist items
01

Sources

ASTM G205-26 listing; ASTM G205-23 listing (historical); ASTM G205-10 listing (historical, original title); Nimonik ASTM G205 listing, the Dropometer product specification and Droplet Lab validation papers.

02

Drafting assistance

Drafted with Claude (Anthropic) from the sources listed, then reviewed by Droplet Lab.

03

What we did not do

We did not copy text from the standard. Buy the current edition for the full procedure.

04

Last checked

October 2026

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References

1. ASTM G205-26. store.astm.org/g0205-26.html
2. ASTM G205-23 listing (historical). store.astm.org/g0205-23.html
3. ASTM G205-10 listing (historical, original title). store.astm.org/g0205-10.html
4. Nimonik ASTM G205 listing. standards.nimonik.com/products/astm/g205/
5. Droplet Lab. Peer reviewed validation papers in Review of Scientific Instruments and Colloids and Surfaces A. dropletlab.com/validation/publications/
6. Droplet Lab. Dropometer product specification, 2026. dropletlab.com/products/dropometer/