Effect of Substrate Preparation and the Conversion Coating on the Corrosion Resistance in Ringer's Solution of 304L Stainless Steel Coated with Alumina Film

Pereira, Carlos M. S.; Silva, Gustavo F.; Diniz, Marília G.; Silva, Camila S.; Braga, Antônio V. C.; Senna, Lilian F. de

doi:10.1590/1980-5373-MR-2024-0044

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Articles • Mat. Res. 27 (Suppl 1) • 2024 • https://doi.org/10.1590/1980-5373-MR-2024-0044 copy

Effect of Substrate Preparation and the Conversion Coating on the Corrosion Resistance in Ringer's Solution of 304L Stainless Steel Coated with Alumina Film

Authorship SCIMAGO INSTITUTIONS RANKINGS

This work aims to determine the best substrate preparation and conversion coatings that may enhance the anti-corrosive performance of alumina film/stainless steel substrate systems in Ringer’s solution. Boehmite, silica, silica/boehmite, and boehmite/silica conversion coatings were deposited on sanded or sandblasted 304L stainless steel samples, and the best results were further covered with alumina film for a long-time exposure evaluation. The best anti-corrosive performances for each substrate preparation were observed for the sandblasted sample covered with silica/boehmite conversion coating (JSB500) and the sanded sample covered with silica (LS500), which showed the highest global resistance (R_g) values (828 Ω.cm² and 1837 Ω.cm², respectively) and the smallest values of global capacitance, C_g (2.19 X 10^-6 F.cm^-2 and 3.37 X 10^-9 F.cm^-2, respectively). After covering with the alumina film and evaluating for 216 h in the corrosive medium, it was noted an increase in the R_g values for both systems (JSBA500 and LSBA500), likely due to the presence of a corrosion products layer. The presence of iron oxides in these conversion coatings led to a more stable alumina film. Comparing the selected coating systems, the LSBA500 exhibited an improved performance, reaching an increase of 85% in R_g and a decrease of 94% in C_g.

Keywords:
Corrosion; Conversion coatings; Roughness; Surface preparation

Sample	Substrate preparation	Conversion coating
J-SS	Sandblasted	-
JB500	Sandblasted	Boehmite
JS500	Sandblasted	Silica
JSB500	Sandblasted	Silica/Boehmite
JBS500	Sandblasted	Boehmite/Silica
L-SS	Sanded	-
LB500	Sanded	Boehmite
LS500	Sanded	Silica
LSB500	Sanded	Silica/Boehmite
LBS500	Sanded	Boehmite/Silica

Chemical	Quantity (g.L^-1)
NaCl	6.80
KCl	0.40
CaCl₂	0.20
MgSO₄ 7H₂O	0.20
NaH₂PO₄ H₂O	0.14
NaHCO₃	2.20
Glucose	1.00

Conversion coating	Sanded (L)			Sandblasted (J)
Conversion coating	R_a (μm)	R_a increase (%)	h (μm)	R_a (μm)	R_a increase (%)	h (μm)
SS	0.068 ± 0.019	-	-	2.160 ± 0.272	-	-
B500	0.249 ± 0.075	266	0.925 ± 0.020	2.484 ± 0.181	15.0	1.226 ± 0.200
S500	0.278 ± 0.094	309	0.568 ± 0.011	2.280 ± 0.132	5.54	0.985 ± 0.019
SB500	0.232 ± 0.014	240	1.180 ± 0.025	2.612 ± 0.270	20.9	2.513 ± 0.008
BS500	0.242 ± 0.072	255	1.008 ± 0.045	2.541 ± 0.303	17.6	1.502 ± 0.060

SAMPLES	R_o	R₁	N₁	R₃	N₂	R_g	C₁	C₃	C_g	Circuit	χ²
SAMPLES	Ω	kΩ cm²	N₁	kΩ cm²	N₂	kΩ cm²	F cm^-2	F cm^-2	F cm^-2	Circuit	χ²
L-SS	35.6	9.15	0.711	8.15	0.784	17.3	5.82 x 10^-6	9.67 x 10^-7	8.29 x 10^-7	[R(RQ)(RQ)]	0.0021
LB500	36.5	13.9	0.806	981	0.804	995	2.14 x 10^-6	9.67 x 10^-7	6.66 x 10^-7	[R(RQ)(RQ)]	0.0019
LS500	30.4	15.8	0.803	1821	0.755	1837	1.17 x 10^-4	3.38 x 10^-9	3.37 x 10^-9	[R(RQ)(RQ)]	0.0022
LSB500	34.4	9.87	0.796	383	0.713	393	1.69 x 10^-4	1.72 x 10^-7	1.72 x 10^-7	[R(RQ)(RQ)]	0.0016
LBS500	71.1	9.65	0.822	143	0.554	153	4.92 x 10^-6	4.90 x 10^-7	4.46 x 10^-7	[R(RQ)(RQ)]	0.0014
J-SS	27.6	10.2	0.807	-	-	10.2	1.19 x 10^-4	-	1.19 x 10^-4	R(RQ)	0.0034
JB500	34.4	9.95	0.700	159	0.808	68.2	9.03 x 10^-6	3.16 x 10^-5	7.55 x 10^-6	[R(RQ)(RQ)]	0.0011
JS500	22.7	9.21	0.758	152	0.774	61.0	1.53 x 10^-4	9.04 x 10^-5	5.69 x 10^-5	[R(RQ)(RQ)]	0.0009
JSB500	25.5	10.0	0.701	818	0.704	828	2.97 x 10^-5	2.36 x 10^-6	2.19 x 10^-6	[R(RQ)(RQ)]	0.0027
JBS500	20.7	10.6	0.706	134	0.792	44.1	2.90 x 10^-5	1.47 x 10^-5	9.77 x 10^-6	[R(RQ)(RQ)]	0.0016

SAMPLES	R_o	R₁	N₁	R₂	N₂	R₃	N₃	R_g	C₁	C₂	C₃	C_g	Circuit	χ²
SAMPLES	Ω	kΩ cm²	N₁	kΩ cm²	N₂	kΩ cm²	N₃	kΩ cm²	F cm^-2	F cm^-2	F cm^-2	F cm^-2	Circuit	χ²
LSA500 3H	36.3	11.3	0.653	-	-	6.46	0.975	17.8	1.64 x 10^-6	-	8.58 x 10^-6	1.38 x 10^-6	[R(RQ)(RQ)]	0.0019
LSA500 24H	38.0	5.55	0.816	0.370	0.642	146	0.615	152	5.92 x 10^-6	7.52 x 10^-10	1.31 x 10^-5	7.52 x 10^-10	[R(RQ)(RQ)(RQ)]	0.0018
LSA500 48H	48.1	4.46	0.642	0.203	0.853	178	0.656	183	4.90 x 10^-7	2.66 x 10^-7	2.92 x 10^-5	1.73 x 10^-7	[R(RQ)(RQ)(RQ)]	0.0038
LSA500 72H	49.3	3.43	0.565	0.389	0.838	183	0.620	187	1.30 x 10^-7	1.56 x 10^-7	2.18 x 10^-5	7.07 x 10^-8	[R(RQ)(RQ)(RQ)]	0.0054
LSA500 144H	54.1	2.38	0.667	0.658	0.851	234	0.598	237	9.47 x 10^-7	9.80 x 10^-8	1.63 x 10^-5	8.88 x 10^-8	[R(RQ)(RQ)(RQ)]	0.0064
LSA500 168H	56.6	2.69	0.663	0.680	0.860	138	0.642	141	1.01 x 10^-6	9.73 x 10^-8	3.37 x 10^-5	8.85 x 10^-8	[R(RQ)(RQ)(RQ)]	0.0016
LSA500 192H	52.6	2.30	0.674	0.677	0.859	219	0.604	222	9.46 x 10^-7	9.28 x 10^-8	1.78 x 10^-5	8.41 x 10^-8	[R(RQ)(RQ)(RQ)]	0.0072
LSA500 216H	53.2	2.41	0.649	0.662	0.851	120	0.648	123	1.03 x 10^-6	9.36 x 10^-8	3.76 x 10^-5	8.56 x 10^-8	[R(RQ)(RQ)(RQ)]	0.0070
JSBA500 3H	30.3	1.02	0.614	-	-	27.3	0.526	28.3	2.86 x 10^-6	-	2.38 x 10^-6	1.30 x 10^-6	[R(RQ)(RQ)]	0.0041
JSBA500 24H	38.8	1.14	0.598	0.440	0.563	89.0	0.598	90.6	2.33 x 10^-6	1.87 x 10^-7	2.21 x 10^-5	1.72 x 10^-7	[R(RQ)(RQ)(RQ)]	0.0095
JSBA500 48H	50.1	0.932	0.599	0.422	0.618	78.6	0.651	80.0	3.22 x 10^-6	2.89 x 10^-6	5.20 x 10^-5	1.48 x 10^-6	[R(RQ)(RQ)(RQ)]	0.0046
JSBA500 72H	48.8	1.23	0.616	0.207	0.882	74.1	0.652	75.5	3.47 x 10^-6	3.02 x 10^-4	6.14 x 10^-5	3.25 x 10^-6	[R(RQ)(RQ)(RQ)]	0.0047
JSBA500 144H	55.4	0.945	0.663	0.436	0.599	90.5	0.663	91.9	4.64 x 10^-5	3.34 x 10^-6	7.74 x 10^-5	3.00 x 10^-6	[R(RQ)(RQ)(RQ)]	0.0050
JSBA500 168H	56.3	0.495	0.586	0.249	0.890	70.0	0.684	70.7	3.59 x 10^-6	2.23 x 10^-4	9.49 x 10^-5	3.40 x 10^-6	[R(RQ)(RQ)(RQ)]	0.0052
JSBA500 192H	58.9	1.57	0.606	0.277	0.876	60.6	0.772	62.4	2.20 x 10^-6	2.41 x 10^-4	2.63 x 10^-5	2.17 x 10^-6	[R(RQ)(RQ)(RQ)]	0.0060
JSBA500 216H	53.2	0.471	0.581	0.228	0.891	59.5	0.686	60.2	4.07 x 10^-6	2.30 x 10^-4	1.08 x 10^-4	3.85 x 10^-6	[R(RQ)(RQ)(RQ)]	0.0060

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