Can an Inorganic Zinc Silicate Coating Be Repaired with Itself?

Repair recommendations for IOZ silicate coatings can range from complete removal to repair with epoxy zinc or surface-tolerant epoxy coatings.⁸ In fact, with a few extra considerations that differ from the repair of other coating types, an IOZ silicate coating can be recoated with itself, although this requires skill and care.

If the coating is found to be too thin after application and an extra coat is required, the silicate solution from any repair coat will migrate into the voids and leave a friable and powdery surface if the surface porosity has not had a chance to fill with corrosion products. The liquid content of the repair coat should be increased by 10 to 15% so there is sufficient liquid to prevent the surface layer from becoming underbound and lacking in adhesion.

Once the coating has aged, porosity is no longer an issue. As with any other repair coating, the surface must be properly cleaned before applying a topcoat of IOZ. As long as the surface is thoroughly clean and free from loose contamination, it will be suitable for overcoating. An IOZ coating can be repaired with either solvent-borne or water-borne IOZ silicate coating, which will perform better than alternatives. The solvent-borne IOZ has better wetting characteristics and is easier to apply in the field, and therefore is recommended as long as humidity conditions are suitable. The initial adhesion immediately after application of a repair IOZ coating is poor,⁶ but once the repair coating is thoroughly cured (which may take several months), an adherent bond develops between the new and old coatings, as shown in Figure below.

Repair coats develop good adhesion after several weeks.

Article copy from: https://www.materialsperformance.com/articles/coating-linings/2016/06/what-do-you-know-about-inorganic-zinc-coatings

Author: ROB FRANCIS is the principal at R A Francis Consulting Services, Melbourne, VIC, Australia, e-mail: robfrancis766@gmail.com. He has more than 40 years of academic, industrial, and consulting experience in metals, materials, and corrosion, particularly regarding selection, specification, and inspection of protective coatings. He has a Ph.D. in corrosion science from the Corrosion and Protection Centre at the University of Manchester, is a NACE-certified Coating Inspector and instructor, and edited the book, Inorganic Zinc Coatings—History, Chemistry, Properties, Applications and Alternatives in 2013. He is a 16-year member of NACE International.

 

Conductivity Test for metallic abrasive, is it possible?

Hi, my friend ask me about conductivity test on metallic abrasive? is it possible? what is the reference?

let’s share..

as my understanding, there are two standard usually used for conductivity test, they are ISO 11127-6 for non-metallic abrasive and ASTM D 4940 for either metallic or non-metallic abrasive.

first, for non-metallic abrasive.

you can check definition of non-metallic abrasive on SSPC-AB1. including maximum allowable conductivity which are 1000 microsiemens per centimeters, see paragraph 4.1.4, when tested with ASTM D 4940. take note that 1000 microS/cm = 1000 microho/cm = 100 miliSiemens/meter. but, always check with your client specification whether its mention about maximum conductivity or not, if not, then you can use this reference standard.

other reference for specification and definition of non-metallic abrasive can find on ISO 11126. this standard will devide each specific product characteristic, i.e. silica, copper slag, garnet, etc. including the maximum allowable conductivity is mention there.

now for the conductivity test method, you can refer to ISO 11127-6 “test method for non-metallic abrasive, determination of water-soluble contaminants by conductivity measurement” or ASTM D 4940 “conductimetric analysis of water soluble ionic contamination of Blasting Abrasives”. both standard are applicable for non-metallic abrasive. anyway, for step by step method activity can clearly find in those standard, through section procedure, i will not explain here.

so why in SSPC-AB1 mention to use ASTM D 4940 not ISO 11127-6? honestly, for me it does not matter, as long both of those standard are used for conductivity test of non-metallic abrasive. then it will depends on your available equipment or client specification requirement.

second, for metallic abrasive.

almost same with non-metallic abrasive, you can check definition of metallic abrasive on SSPC-AB3. the maximum allowable conductivity also same 1000 microS/cm = 1000 microho/cm = 100 miliSiemens/meter, see paragprah 4.2.2, when tested with ASTM D 4940. again, always check with your client specification whether its mention about maximum conductivity or not, if not, then you can use this reference standard.

other reference for specification and definiton of metallic abrasive can find on ISO 11124. there will explain about specification and classification of metallic abrasive. but take note, you will not find any statement related to conductivity requirement.

for method, as per scope of ISO 11127-6 mention this standard is used to check conductivity on non-metallic abrasive. so, it is not proper if use this standard to check conductivity of metallic abrasive. the only standard able to check conductivity of metallic abrasive is ASTM D 4940 as it also mention in SSPC-AB3 paragraph 5.2.7. again, step by step method acitivity can clearly find in that standard.

so, is it possible to do conductivity test for mettalic abrasive? YES, the requirement clearly mention on SSPC-AB3 and you can use ASTM D 4940 for testing procedure.

Bagus Rengga Ludfianto
NACE CIP Level 3
Indonesia

 

DFT Calibration, ROUGH or FLAT surface

hi,

many people (inspector or engineer) doubt about DFT calibration. is it need to calibrated on flat surface or rough surface? want to know my opinion?

let’s share…

eventhough there are so many standard for DFT calibration, but in this article i only use two common standard, which are ISO 19840 and SSPC-PA2.

first, lets discuss about ISO 19840.

in ISO 19840 it is generally explained through paragraph 5.3 “material used for calibration are plastic shim, un-coated or pre-coated test plate” and paragraph 6.2 “adjustment of the instrument shall be carried out on un-coated test plate at zero with shims/foils below and above the specified DFT or in pre-coated test plates instead of verified shims/foils”.

the word un-coated test plate are describe as smooth, flat, clean free millscale, etc.

while the pre-coated test plate are describe as certified, smooth, flat, visually clean pre-coated steel test plates with assigned values traceable to recognised standards and with coating thicknesses near to the expected dry film thickness to be measured.

the calibration method are as follows:

1. prepared un-coated flat test plate surface, i suggest you to use the un-coated test instead of pre-coated test plate due to pre-coated surface with values traceable to recognised standard is hard to obtain, and if available it is costly :).
2. prepare shims/foils similar with specified DFT required. take 1 shims/foils which is near the specified DFT.
3. select calibration method on your gauge. i suggest using zero method.
4. place the shims on the un-coated flat test plate surface, and adjust the scale reading to the value of the shims/foils.
5. finish and close the calibration, then back to the DFT reading panel. try to measure the shims/foils once again on the un-coated flat test plate surface.
6. you have done your calibration on the un-coated flat test plate surface.

calibration on un-coated flat surface is required correction factor when it use to measure paint thickness on blasted/rough surface. flat surface calibration will give false paint thickness reading on blasted surface since the blasted surface characteristic having peak and valley point.

the DFT gauge will measure mean of the paint thickness on blasted surface area higher than actual because there are distance from valley of the blasted surface to the probe. while the actual paint thickness from peak of the blasted surface to the probe are less than specification. in this case, correction value added to reduce effect of the valley point from blasted surface. you will notice in paragraph 7 “correction value” as shown below:

this correction value is related to the blasted profile on your surface. example if you have surface profile on your blasted surface is 65 microns grit, then refer to ISO 8503-1 the grit comparator is between segment 2 to segment 3, so the range of the profile gauge is medium and the correction value to be used is medium or 25 microns.

once you know your correction value, subtracted the value from the individual reading every time you read the DFT of each layer. example, when you place your probe on the primer coat layer, you will see on your DFT gauge 80 microns DFT. this means you have to subtracted 25 microns from 80 microns. so the actual DFT of your primer coat is 80-25 = 55 microns. this correction value is applied on each layer you read the DFT. example on top coat layer is shown 200 microns. this means you have to subtracted 25 microns from 200 microns. so the actual DFT of your top coat is 200-25 = 175 microns. and so on..

optional..

sometimes the question then, if we use this correction value, why the reading film on DFT gauge is less than specification? the answer is YES, because the correction value is only take generally, as a mean.

however, ISO 19840 also mention in Appendix A that calibration also posible to do in rough surface or blasted area.

the calibration method are simple:

1. prepare blasted surface same with actual painting production.
2. prepare shims/foils similir with specified DFT required. take 2 shims/foils which are below (thinner shims) and above (thicker shims) specified DFT.
3. select calibration method on your gauge, i suggest using rough surface/2 points method.
4. place the thinner shims on the blasted surface, and adjust the scale reading to the value of the shims/foils.
5. place the thicker shims on the blasted surface, and adjust the scale reading to the value of the shims/foils.
6. finish and close the calibration, then back to the DFT reading panel. try to measure the shims/foils once again on the blasted surface.
7. you have done your calibration on the blasted surface.

by using this Appendix A method, you dont need to use correction factor, no need to subtracted from the individual reading.

So, either using flat or rough surface is possible in accordance to ISO 19840.

optional, sometimes the question then, why the reading film on DFT gauge is less than specification? the answer is YES, because there are paint loss due to effect of ‘dead volume’.

so, if there are specification mention for primer DFT 75 microns (example volume solid 50%), the WFT should be minimum 150 microns, right? if you use this 150 microns WFT to achieve 75 microns DFT, your DFT reading on the DFT gauge ofcourse will be less. because the paint is absorb in the ‘dead volume’. so then to avoid less reading you have put additional thickness to cover the ‘dead volume’. YES, put additional 25 microns on your new DFT (or depends on you correction value, it may 10 25 or 40 microns). so if the specification mention for primer DFT 75 microns, you have put additional 25 microns DFT to cover the correction value. now the primer DFT should be 75 + 25 microns = 100 microns. and does the WFT will be 200 microns (example VS 50%). by this method you will have DFT reading same to the specification.

(to be continued.. for SSPC-PA2 method, i will update once available, just wait and see..)

 

Painting on Galvanize Surface

One of my friend asking to me, what is suitable paint for Galvanize surface? Because he worried the client spec of using Inorganic Zinc primer with SP2 or SP3 surface preparation is suitable for the galvanize surface. So, what is the best and suitable painting above galvanize?

let’s share..

In my understanding there is no specification address for coating on top of galvanize surface, except for ISO 12944-5 which is only guideline for paint system on top it (please correct me if I am lack

Other standard for Hot Dip Galvanized, ASTM A 123 or ISO 1461 only mention for Coating of steel using Zinc (hot dip galvanized), this standard only s r to build galvanize layer but not for coating on top of galvanize product.

Hence the painting on top of galvanize surface still depend to Paint Manufacture recommendation. Because paint manufacture will be know what is paint product suitable for the galvanize substrate.

There is one specification mention for galvanize “coating repair” surface which is ASTM A 780. This standard scope to give repair method for galvanize surface having damage and lose of the galvanize content thus create a bare metal surface without protection. One of the repair method from this standard is using paint containing zinc with most suitable to Organic Zinc (ASTM A 780 annex A2).

Why not Inorganic Zinc? Because the Inorganic Zinc primer will not suitable with the SP2 or SP3 surface preparation and this will require adequate anchor profile to well adheres.

So, what is suitable paint system over galvanize?

There are two systems suitable for galvanize spec:

1. Suitable as painting and also repair (if client required to ASTM A 780 requirement).
   • Primer : Organic Zinc Primer
   • Second : HB Epoxy
   • Top : Polyurethane
2. Suitable as coating and also repair (if client not required to ASTM A 780).
   • Primer : Surface tolerant Epoxy
   • Top : Polyurethane

 

Internal Painting pada dinding Internal LNG Storage Tank, apakah perlu?

Beberapa hari yang lalu ada pertanyaan dari teman di forum pribadi kami, “Perlukah dinding Internal LNG Storage Tank dipainting untuk perlindungan anti korosinya? Jika, internal tank tersebut memakai steel dengan kadar 9% Nickel.

Diskusi tersebut dilanjutkan dan berikut adalah summarynya, let’s share..

Oke kita bahas dari awal dahulu,

LNG adalah kepanjangan dari Liquefied Natural Gas, atau dalam bahasa indonesia adalah gas alam yang dicairkan, dimana gas alam ini mostly methana. Prosesnya terjadi pada tekanan 100-6000KPa, suhu -160 C.
Proses singkatnya : mengkonversi volume gas di tekanan dan suhu normal menjadi fase liquid dengan volume 1/640 nya.

Dalam proses pencairan ini (perubahan gas menjadi cair), bisa saja ada impurities, impurities bisa saja membuat korosif. Selain itu ingat, di LNG plant ada beberapa proses penting dan korosif, H2O removal, CO2 removal dan H2S removal.

Selanjutnya, untuk material dinding internal LNG Storage Tank dengan kadar 9% Ni, apakah bisa mempengaruhi kekuatan anti korosif dari dinding internal LNG Storage Tank itu sendiri, meskipun tanpa ada tambahan coating/painting?

Memang penambahan Ni pada pembuatan besi/baja main purposenya bukan untuk anti korosi, tapi lebih menjadikan material steel tersebut lebih bagus sifat impact temperaturenya (ingat pada proses pencairan LNG diperlukan suhu -160 C). Dan secara fundamental, material dengan temperature yang sangat rendah (cryogenic material) cenderung lebih stabil dan tidak mudah korosi.

Dalam teori metalurgi, semakin tinggi Ni maka akan semakin meningkatkan fasa austenit, dan semakin rendah Ni akan semakin meningkatkan fasa ferit yang bersifat magnetik. Sifat magnetik tersebut berasosiasi dengan corrosivity (tingkat korosinya).

Penambahan Ni juga memberikan sifat ductile (ulet) pada material dan juga chemical resistance.

Sehingga, penambahan Ni juga bisa dikatakan berhubungan dengan anti korosi.

Jadi dapat disimpulkan disini bahwa material dinding internal LNG Storage Tank dengan kadar 9% Ni akan mengconsider mekanisme passivasi, selain itu high pressure & low temperature pada proses pencairan LNG tersebut akan menjadi penghambat untuk terjadinya korosi.

Sehingga, apakah dapat disimpulkan bahwa dinding internal LNG Storage Tank dengan kadar material 9% Ni tidak memerlukan internal painting/coating?
Kalau saya sih Yes! Tidak perlu!, bagaimana dengan anda? 😁

 

Aplikasi anti-skid pada lapisan coating

Anti-skid atau biasa orang-orang menyebutnya sebagai aggregate banyak digunakan pada proyek-proyek konstruksi (umumnya) bangunan laut. Dimana fungsi anti-skid/aggregate adalah sebagai tambahan atau bagian lapisan coating pada walkway agar orang saat berjalan diatasnya tidak mudah terpeleset.

Anti-skid/aggregate yang umum digunakan adalah garnet, silicon, alumunium oxide. Yang memiliki ukuran (mesh) cukup besar sekitar 1mm-2mm.

Lalu bagaimana cara mengaplikasikan anti-skid/aggregate tersebut pada lapisan coating?
Let’s share..

Oke, sekarang contohnya kita punya suatu sistem lapisan painting dengan konfigurasi,
Primer : epoxy primer 100microns.
Second : epoxy high build 250microns.
Third : epoxy high build 250microns.
Top : polyurethane 50microns.

Lakukan surface preparation seperti biasa kemudian dilanjutkan dengan cat primer 100microns lalu tunggu sesuai interval coating-nya sebelum masuk lapisan kedua. Lanjutkan dengan aplikasi second 250micron lalu tunggu sesuai interval coating-nya sebelum masuk lapisan ketiga.

Lanjutkan aplikasi lapisan ketiga dengan spray tipis sekitar 150microns (dari total 250microns yang seharusnya diaplikasi) dan dilanjutkan dengan menaburkan material anti-skid/aggregate saat cat masih basah.

*Note: metode yang dipakai pada bahasan ini adalah menaburkan anti-skid/aggregate bisa menggunakan alat khusus, atau bisa menggunakan kaleng/botolkosong yang diberi lubang bagian bawahnya, dan jangan menaburkan dengan tangan kosong (memangnya kita mau memberi makan burung, heheee…).

Setelah semua bagian rata ditaburkan anti-skid/aggregate, lanjutkan dengan spray third coat 100microns sisanya.

*Note: saat aplikasi lapisan sisanya ini, jangan sampai melewati waktu wet on wet dari third coat tersebut. Lalu biarkan hingga selesai interval coating-nya sebelum masuk lapisan top coat.
*Note: metode yang lain adalah aplikasi lapisan sisanya ini dilakukan setelah lewat interval coating-nya. Alias tunggu cat sampai kering dulu. Namun kelemahannya jadi lebih lama waktu tunggunya.

Sebelum aplikasi top coat, gunakan sapu untuk menghilangkan debu/partikel kecil dari anti-skid/aggregate yang gampang terlepas. Lalu lanjutkan aplikasi top coat seperti biasa.

Mungkin itu sedikit sharing untuk aplikasi anti-skid/aggregate dari saya,

Salam coating.

 

Glass Syntetic Polyurethane

Baru saja saya baca ada email salah seorang member milist migas indonesia yang menanyakan tentang GSP (GSPU) coating. Tertarik mengetahui lebih jauh, akhirnya saya coba search lebih jauh dan mendapat beberapa ilmu..
Let’s share..

GSP/GSPU (Glass Syntetic Polyurethane) adalah salah satu jenis thermal insulation yang banyak digunakan untuk menjaga aliran/flow dari pipeline tetap seperti yang diinginkan, selain juga tentunya sebagai corrosion protection. Terutama untuk pipeline yang dipakai di offshore laut dalam.
GSP ini merupakan mixing antara glass dengan syntetic polyurethane, sehingga disebut Glass Syntetic PU.
Hal ini dikarenakan pada kedalaman tertentu, pengaruh suhu disekitar pipeline juga akan mempengaruhi flow didalam pipeline tersebut.
Umumnya temperatur yang dimaintain dalam process ini berkisar antara -35 sampai 115 derajat celcius, dengan kedalaman maksimal dibawah 2800 meter (Sumber: Tenaris.com).

Proses aplikasi cukup mudah, sama dengan coating system pada pipeline umumnya, yaitu pipeline yang akan diberikan lapisan GSP awalnya diblasting, kemudian diberikan primer epoxy bonded, baru finalize dengan glass syntetic polyurethane. Maksimum (Sumber: Brederoshaw.com).

 

Type of Coating

Type of Coating based on curing / drying time divided to 3 types :

# Physically curing coating

# Oxidation curing coating

# Chemically curing coating

# Physically curing coating are coating which only cure by evaporation of the solvent. Types of Physically cured coating are : Chlorinated Rubber (CR), Tar / Bitumen / Asphalt, Latex / Emulsion, Vinyl acrylic emulsion

# Oxidation curing coating are coating which cure by evaporation + O2 (oxide/oxidation). Types of Oxidation cured coating are : Alkyd, Epoxy Ester, Phenolic, Phenolic Epoxy

# Chemically curing coating are coating which cure by polymerization (chemically induced – agent solvent). Types of chemically cured coating are :

Epoxy (two component),

• Advantages are : Chemical resistance, Hardness
• AdhesionLimitations are : Overcoat restriction, color, chalking (if used for top coat)
• Usually use for/in : Structural steel, vessel linings

Coal Tar Epoxy,

• Advantages are : Water resistance, chemical resistance
• Limitations are : Fading / chalking, color only black
• Usually used for/in : Crude oil tanks, ship, jetty

Epoxy Emulsion,

• Advantages are : Low solvent color, low toxic, durable
• Limitations are : Reduced water resistance
• Usually used for/in : Sensitive environment

Vinyl Ester / Polyester,

• Advantages are : Excellent gloss, high build, water / acid resistance
• Limitations are : Shrinkage, Reaction unstable, alkaline conditions
• Usually used for/in : Tank linings, FRP (GRP) product

Urethane,

• Advantages are : Water / acid resistance, abrasion resistance, tolerance high RH
• Limitations are : Pack stability, limited adhesion
• Usually used for/in : Offshore platform, topcoat over epoxy, wood/concrete floor

Polyurethane,

• Advantages are : Good chemical/solvent resistance, abrasive resistance, flexibility, color gloss retention
• Limitations are : Isocyanate component as hazardous
• Usually used for/in : Tank Linings, floor finishes, gloss over epoxy

Epoxy Phenolic > specialty heat converting one component

• Usually used for/in : Interior of down hole tubing, process vessels
• Epoxy Phenolic baking schedule : Set up 95’C (200’F), Final 165′-200’C (325′-500’F)

High bake Phenolic : Vinyl (Butyral) Wash Primer (PVB) > specialty primer uses acid to promote adhesion

 

Modem HUAWEI E220

1 Agustus 2012,

Selamat pagi, good morning,

Pagi ini saya ingin share tentang modem HUAWEI E220 yang barusan saya dapat (beli maksudnya, hehee).

Modem ini saya tebus dengan mahar Rp 130rb, (termasuk ongkos kirim dari Depok ke Batam), murahkan? iyalah, kan second, heheee. Tapi meskipun second, barangnya masih bagus bro, meskipun pembeliannya dari tahun 2010 lho (ada di sticker garansinya). Modem yang saya beli ini terdaftar dengan label “OPTUS”, meskipun saya gak tau apa itu OPTUS, tapi saya yakin ini modem bagus. hehee.. Malam saya transfer uangnya ke seller, selisih 2 hari datang deh modemnya.

Modem datang, langsung saya tes pake kartu tri 3 paket bulanan 500mb. awalnya terasa respon modem berat, susah connectnya, sering putus. akhirnya dengan segala keterbatasan (alah bahasanya) saya coba browsing problemnya. Baca sana sini, ternyata ada yang nyaranin harus update firmware “E220_11.313.02.00.01.B268_Firmware_Update.rar”, dan “Mobile_Partner_11.302.09.01.539_Voice_USSD.zip”. Okelah akhirnya saya coba download firmware2 tadi, dan… eng ing eng, modem langsung lancar dipakenya. kalau untuk ngeblog aja boleh lah modem ini.

Kata orang sih modem ini udah support MDMA (bisa dikodokin), tapi saya pun belum tau artinya apa, hehee. Yang jelas modem ini jalan dengan speed 7,2 Mbps, mantaplaaahh (meskipun koneksi saya cuma mentok di 384 Kbps, jadi tulisan 7,2 Mbps itu cuma hiasan aja,hehee). Modemnya mantap, adem, gak putus2, recomended lah. Cuma ada kurangnya, gak support external antenna coy.

Okelah sampe sini dulu cerita tentang Huawei E220, mau kerja dulu.

 

New Welding in an Existing Welding Line (For Repair or Rebuild)

Dear all, this is a sharing from a member of KMI (Indonesia Oil and Gas Community).

The case is,
There is a retubing process for power boiler. Then the client ask to vendor/contractor for cutting the old tube and replace with new one.
The problem is position of cutting for old tube will be same as the new welding line. So, the new welding line position will be same as previous welding joint line existing which got cutting.

Usually, we avoid new welding joint in existing welding line. Some people said that welding in an existing welding line will make structure is not good. Because of microstructure in HAZ will be change, and structure become hardness due to welding process more than one. But if we considering of basic normalishing, it doen’t matter as long as we keep the cooling rate, so that automatically the microstructure will not changed.

But, actually are there any code or rule for that condition? Or, what is the risk if we do that?

And, Yes, ASME allow it. We can refer to ASME VIII; UW-14 (for Pressure Vessel). For Power Boiler refer to ASME I; PW-14. And UW-38 for remove defect.

Beside that, practically it just a simple case. We can cut old tube, ground out old weld joint line and also clean out. Then we do a NDT test to see the crack or defect. If material okay, we can weld it with new tube.

Source : Summary of Indonesia Oil and Gas Mailing List.